Synthesis and properties of azole-substituted ferrocenes

Article abstract of DOI:10.1016/j.jorganchem.2006.08.020

4-Ferrocenyltriazole, 4-(4-ferrocenylphenyl)triazole, 4-ferrocenyltetrazole, and 4-(4-ferrocenylphenyl)tetrazole have been prepared. Redox potentials and decomposition temperatures were evaluated and all the compounds were crystallographically characterized; in most cases, weak intermolecular CH?N hydrogen bonds (H?N dist. = 2.3-2.5 ?) were formed between the azole moieties. Two polymorphs were found for 4-ferrocenyltetrazole, formed with either CH?N or π-π interactions.

Full text of DOI:10.1016/j.jorganchem.2006.08.020

Journal of Organometallic Chemistry 691 (2006) 4882–4889
www.elsevier.com/locate/jorganchem
Synthesis and properties of azole-substituted ferrocenes
a,b,
a
a
a
Tomoyuki Mochida
*, Hirotaka Shimizu , Shinya Suzuki , Takahiro Akasaka
a
Department of Chemistry, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan
Research Center for Materials with Integrated Properties, c/o Faculty of Science, Toho University, Japan
b
Received 3 April 2006; received in revised form 1 August 2006; accepted 11 August 2006
Available online 22 August 2006
Abstract
4-Ferrocenyltriazole, 4-(4-ferrocenylphenyl)triazole, 4-ferrocenyltetrazole, and 4-(4-ferrocenylphenyl)tetrazole have been prepared.
Redox potentials and decomposition temperatures were evaluated and all the compounds were crystallographically characterized; in
˚
most cases, weak intermolecular CHꢀ ꢀ ꢀN hydrogen bonds (Hꢀ ꢀ ꢀN dist. = 2.3–2.5 A) were formed between the azole moieties. Two poly-
morphs were found for 4-ferrocenyltetrazole, formed with either CHꢀ ꢀ ꢀN or p–p interactions.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Ferrocene; Tetrazole; Triazole; Crystal structures; Hydrogen bond; Redox potentials
1. Introduction
(4-ferrocenylphenyl)-1H-tetrazole (FcPhTe). These mole-
cules are expected to be useful for the development of
multi-functional metal assemblies such as spin-crossover
complexes [7]. As a related example, 5-ferrocenyl-2H-tetra-
zole [8] is known, which is a C-substituted tetrazole having
an NH proton.
Tetrazoles and their metal salts are known as explosives
[9,10], so we used thermogravimetric analysis to evaluate
the thermal decomposition behavior of our molecules. To
date, only a few crystal structures of N-aryl triazoles and
tetrazoles have been reported; therefore, our compounds
were fully characterized crystallographically, and the
importance of weak CHꢀ ꢀ ꢀN hydrogen bonds to their crys-
tal architectures was revealed. Weak intermolecular inter-
actions in organic crystals are of interest from the
viewpoint of organic crystal engineering [11,12].
Organometallic supramolecular assemblies have
attracted special attention in recent decades [1,2]; heteroa-
ryl-substituted ferrocene ligands provide a useful approach
towards their synthesis. For this purpose, we have designed
a variety of ligands, which are shown in Chart 1 [3,4].
These versatile ligands give topologically diverse assembled
structures when combined with various metal salts; the
modes of assembly depend on the number and position
of the ligands’ nitrogen coordination sites.
To extend the study, we designed the azole-substituted
ferrocenes shown in Chart 2. Azole substituents provide
versatile ligating sites so have the potential to form a vari-
ety of metal complexes [5]. Their chemistry has been the
subject of intense development with applications in medi-
cine, biology, agriculture, and other fields [6]. We report
here the preparation and properties of 4-ferrocenyl-4H-
[1,2,4]triazole (FcTr), 4-(4-ferrocenylphenyl)-4H-[1,2,4]tri-
azole (FcPhTr), 4-ferrocenyl-1H-tetrazole (FcTe), and 4-
2. Results and discussion
2.1. Preparation
The azole-substituted ferrocenes could be prepared by
methods analogous to those used for the preparation of
N-aryl triazoles, but the yield was generally lower. In par-
ticular, the yield of the ferrocenyl derivatives (FcTr and
*
Corresponding author. Address: Department of Chemistry, Faculty of
Science, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan.
Fax: +81 47 472 4406.
E-mail address: mochida@chem.sci.toho-u.ac.jp (T. Mochida).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.08.020

T. Mochida et al. / Journal of Organometallic Chemistry 691 (2006) 4882–4889
4883
1,2-diformylhydrazine [13,14]; therefore, we first applied
this method but it turned out to be less suitable for ferroce-
nyl derivatives. Thus, condensation of aminoferrocene with
1,2-diformylhydrazine afforded FcTr, but only in a poor
yield (yield 5%), and this reaction produced ferrocenylfor-
mamide [15] (yield 37%) as the main product. This method
was also applied to the preparation of FcPhTr, but the
yield was again low (15%). As an alternative method,
FcPhTr could be prepared by Negishi coupling (Scheme
1(b)): the reaction of ferrocenylzinc chloride with 4-(4-iod-
ophenyl)triazole in the presence of a palladium catalyst
gave the desired compound in a 38% yield.
FcTe and FcPhTe were prepared by applying a standard
method [16], the reaction of amino precursors with sodium
azide and trimethyl orthoformate in acetic acid (yields 56%
and 68%, respectively, Scheme 1(c)).
Chart 1.
In the above reactions, 4-ferrocenylaniline was the start-
ing material for FcPhTe and FcPhTr. 4-Ferrocenylaniline
can be synthesized by diazo-coupling of 4-nitrophenyldiazo-
nium salt with ferrocene, followed by reduction [17,18], but
we found that the use of Negishi coupling – coupling of ferr-
ocenylzinc chloride with 4-iodoaniline in the presence of a
palladium catalyst – was more convenient and resulted in
a higher yield (29%) then the conventional method.
2.2. Redox potentials
The electrochemical properties of these compounds were
measured by means of cyclic voltammetry in acetonitrile
solution. Reversible redox waves of the ferrocenyl moieties
were observed in all the compounds, as listed in Table 1 (vs.
FeCp2=FeCp2þ). The half-wave potentials of FcTr and
FcTe were 0.21 V and 0.27 V, respectively, and those for
FcPhTr and FcPhTe were 0.07 V and 0.09 V, respectively.
The higher redox potentials of the former group are attrib-
uted to the stronger electron-withdrawing effects of azole
groups compared with phenyl groups. The redox potential
of FcTe is higher than that of FcTr. This is ascribable to
the stronger electron-withdrawing effect of tetrazole, which
contains one more nitrogen atom than triazole. This effect
becomes less significant when phenylene groups are pres-
ent, as seen by the more similar redox potentials of FcPhTe
and FcPhTr.
Chart 2.
FcTe) were lower than those of the ferrocenylphenyl ones
(FcPhTr and FcPhTe).
FcTr and FcPhTr were prepared most conveniently by
the condensation of aminoferrocene or ferrocenylaniline
with N,N-dimethylformamide azine dihydrochloride in
the presence of p-toluenesulfonic acid (Scheme 1(a); yields
45% and 81%, respectively). N-Aryl triazoles are usually
prepared in high yields by the condensation of anilines with
2.3. UV–Vis spectra
UV–Vis spectra of the compounds in acetonitrile solu-
tion are shown in Fig. 1 and the spectral data are listed
Table 1
þ
Redox potentials (in V vs. FeCp2=FeCp2
)
Epc
Epa
E1/2
FcTr
FcTe
FcPhTr
FcPhTe
0.17
0.24
0.04
0.06
0.24
0.30
0.10
0.12
0.21
0.27
0.07
0.09
Scheme 1.
In 0.1 M nBu4NClO4–MeCN.

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T. Mochida et al. / Journal of Organometallic Chemistry 691 (2006) 4882–4889
2.4. Thermogravimetric analysis
To examine the thermal decomposition behavior of
these compounds, we performed thermogravimetric (TG)
analysis on powder samples. The TG curves are shown in
Fig. 2. The temperatures at which weight loss exceeded
5% were 474 K (FcTe), 477 K (FcPhTe), 520 K (FcTr),
and 545 K (FcPhTr). The tetrazole ligands were less ther-
mally stable than the triazole ones, as anticipated. The
TG curves for the tetrazoles (FcTe and FcPhTe) showed
a sudden weight loss at around 480 K, which continued
up to about 485 K, of 14% and 10%, respectively. If this
is attributable to the evolution of N2 gas, it corresponds
to a loss of ca. 60% of the N atoms from each molecule.
The weight loss for triazoles (FcTr and FcPhTr) occurred
more gradually at higher temperatures; for these molecules,
the loss of one N2 molecule corresponds to a weight loss of
11% and 9%, respectively, which was seen only above
550 K.
The decomposition temperatures were somewhat higher
for ferrocenylphenyl azoles (FcPhTe and FcPhTr) than for
ferrocenyl azoles (FcTe and FcTr), which indicates that the
presence of the phenylene group increases thermal stability.
It has been reported that decomposition temperatures of
phenyltetrazoles are about 430–490 K and that the pres-
Fig. 1. UV–Vis spectra of azole-substituted ferrocenes in acetonitrile. The
spectra are vertically shifted.
in Table 2. As seen in Fig. 1, the spectra of FcTr and FcTe
are almost the same, with weak absorptions in the visible
region. The absorption bands below 280 nm are assignable
to Fe(d)–p* and p–p* transitions. Similarly, the spectra of
FcPhTr and FcPhTe are almost the same. These com-
pounds were more strongly colored than FcTr and FcTe
and exhibit stronger absorption bands at low energies,
due to extended conjugation. The bands below 320 nm
and around 350 nm are mainly assignable to p–p* and
Fe(d)–p* transitions, respectively. Very broad weak
absorption bands were observed at around 430 nm in FcTr
and FcTe, and at around 450 nm in FcPhTr and FcPhTe.
These bands are assignable to d–d transitions [19], the lat-
ter probably being mixed with Fe(d)–p* transitions. In both
series, the absorption bands for tetrazoles are slightly red-
shifted with respect to the triazoles. This is ascribable to the
lower LUMO energy of the tetrazole system, which is con-
sistent with the stronger electron-withdrawing effect of the
former as revealed by the electrochemical results.
Table 2
UV–Vis absorption data in acetonitrile
Compounds
k )
max/nm (e/Mꢁ1 cmꢁ1
FcTr
FcTe
FcPhTr
207 (19578), 263 (4078), 426 (126)
204 (21118), 269 (4312), 312 (885), 432 (155)
212 (24249), 248 (16980), 286 (16514), 337 (2200),
449 (504)
FcPhTe
211 (22349), 253 (13608), 290 (15668), 352 (2444),
451 (631)
Fig. 2. TG curves for azole-substituted ferrocenes.

T. Mochida et al. / Journal of Organometallic Chemistry 691 (2006) 4882–4889
4885
ence of an electron-releasing substituent on the tetrazole
ring leads to higher thermal stability [10]. The electron-
releasing ferrocenyl substituent might contribute to stabil-
ity but the effect was not remarkable.
2.5. Crystal structures
Fig. 3. Schematic illustration of weak hydrogen bonds in FcTr (X = CH)
Structures of all the compounds were determined by X-
ray crystallography. Crystallographic parameters are listed
in Table 3. In most crystals, significant intermolecular con-
tacts were found between the azole moieties: one of the
azole hydrogens has a CazoleHꢀ ꢀ ꢀNazole interaction with
the N atom of the adjacent molecule (Fig. 3). The Hꢀ ꢀ ꢀN
distances in the ferrocenyl azoles (FcTr and FcTe) were
and FcTe (X = N, a-form).
˚
˚
about 2.3 A, which is shorter by 0.4 A than the sum of
the van der Waals distances so can be regarded as weak
hydrogen bonds [11]. The corresponding distances in ferr-
ocenylphenyl azoles (FcPhTr and FcPhTe) were somewhat
˚
longer (about 2.5 A). Other intermolecular contacts were
less significant.
Fig. 4 shows the packing diagram of FcTr. In this mol-
ecule, the dihedral angle between the Cp and tetrazole rings
is 38.5(1)ꢁ. The triazole moieties form a chain arrangement
˚
via the CHꢀ ꢀ ꢀN interaction (Hꢀ ꢀ ꢀN distance: 2.33 A) along
the b-axis, as indicated by dashed lines in the figure. No
intermolecular p–p interaction exists, due to the nearly
orthogonal intermolecular arrangement of the ferrocenyl
moieties.
FcTe afforded two polymorphs, the a-form, from
methanol, and the b-form, from acetone. The contrasting
packing interactions in these polymorphs are of interest:
the CHꢀ ꢀ ꢀN interaction prevails in the a-form, while the
b-form shows a p–p stacking interaction. Fig. 5(a) shows
Fig. 4. Packing diagram of FcTr viewed along the a-axis. Hydrogen atoms
are omitted for clarity. Nitrogen atoms are shaded. CHꢀ ꢀ ꢀN interactions
are indicated by dotted lines.
Table 3
Crystallographic data
FcTr
FcTe (a-form)
FcTe (b-form)
FcPhTr
FcPhTe
Empirical formula
Formula weight
Crystal size (mm3)
Crystal system
C
253.09
12H11FeN3
C11H10FeN4
254.08
0.60 · 0.20 · 0.05
Orthorhombic
10.4150(7)
C11H10FeN4
254.08
C36H30Fe2N6
658.36
C17H14Fe1N6
330.17
0.50 · 0.30 · 0.30
Monoclinic
13.4137(7)
10.2518(5)
7.5076(4)
92.9010(10)
1031.08(9)
P21/c
0.37 · 0.13 · 0.06
Monoclinic
5.7175(5)
19.8247(17)
8.8152(8)
94.646(2)
995.90(15)
P21/n
0.40 · 0.20 · 0.20
Monoclinic
22.801(2)
13.4359(14)
9.5969(10)
99.847(2)
2896.7(5)
P21/c
0.25 · 0.13 · 0.13
Monoclinic
12.3356(10)
6.3641(5)
18.1773(15)
97.8140(10)
1413.8(2)
P21/n
˚
a (A)
˚
b (A)
7.3714(5)
26.7255(18)
˚
c (A)
b (ꢁ)
3
˚
V (A )
2051.8(2)
Pbca
Space group
Z value
4
1.63
1.433
520
8
4
4
4
Dcalc (g cmꢁ3
)
1.645
1.443
1040
1.695
1.487
520
1.510
1.040
1360
1.551
1.067
680
l (mmꢁ1
F(000)
)
No. of reflections
No. of observations
Parameters
7504
2547
145
14297
2537
145
7361
2479
145
21258
7203
517
8507
3228
235
Temperature (K)
Final R1, Rw (I > 2r)
Final R1, Rw (all data)
Goodness-of-fit
173
173
173
173
150
0.0289, 0.0762
0.0297, 0.0771
1.007
0.0322, 0.0797
0.0397, 0.0872
1.03
0.0643, 0.1257
0.0700, 0.1228
0.971
0.0446, 0.0910
0.0962, 0.1129
0.986
0.0400, 0.0865
0.0771, 0.1008
1.022

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T. Mochida et al. / Journal of Organometallic Chemistry 691 (2006) 4882–4889
Fig. 6. Packing diagrams of (a) FcPhTr and (b) FcPhTe. Hydrogen atoms
are omitted for clarity. Nitrogen atoms are shaded. CHꢀ ꢀ ꢀN interactions
are indicated by dotted lines.
Fig. 5. Packing diagrams of FcTe: (a) a-form and (b) b-form, viewed
along the b-axes. Hydrogen atoms are omitted for clarity. Nitrogen atoms
are shaded. CHꢀ ꢀ ꢀN interactions are indicated by dotted lines.
the packing diagram of the a-form, the molecular
arrangement of which resembles that of FcTr. The tetra-
zole moieties form a chain arrangement via the CHꢀ ꢀ ꢀN
lene and triazole rings [41.1(2)ꢁ and 4.8(2)ꢁ, respectively],
while those between the Cp and phenylene rings are
comparable [18.9(2)ꢁ and 19.8(2)ꢁ]. The CHꢀ ꢀ ꢀN interac-
tion connects molecules A and B (Hꢀ ꢀ ꢀN distance:
˚
interaction (Hꢀ ꢀ ꢀN distance: 2.34 A) along the a-axis, and
˚
no intermolecular p–p interaction exists due to the nearly
orthogonal arrangement of the ferrocenyl moieties. The
intramolecular dihedral angle between the Cp and tetra-
zole rings is 38.7(2)ꢁ. Fig. 5(b) shows the packing dia-
gram of the b-form. The intramolecular dihedral angle
between the Cp and tetrazole rings is 12.5(2)ꢁ, which is
much smaller than for the a-form. The b-form exhibits
no chain-like arrangement of the tetrazole moieties, but
rather a stacking structure along the c-axis, accompanied
by intermolecular p–p interactions between the Cp ring
and the tetrazole ring. Thus, the polymorphism depends
on whether CHꢀ ꢀ ꢀN interactions or p–p stacking interac-
tions dominate.
As seen above, the packing structures of FcTr and
FcTe (a-form) are governed by CHꢀ ꢀ ꢀN interactions.
However, when phenylene spacers are introduced, the
p–p interactions prevail and the CHꢀ ꢀ ꢀN interaction
becomes less significant. Fig. 6(a) shows the packing dia-
gram of FcPhTr. The crystal contains two crystallo-
graphically independent molecules, denoted A and B,
which have different dihedral angles between the pheny-
2.48 A); the interaction is local and no network is
formed. Some p–p interactions are observed between
the molecules. Fig. 6(b) shows the packing diagram of
FcPhTe. The dihedral angle between the phenylene and
tetrazole rings is 5.3(1)ꢁ, and that between the Cp and
phenylene rings is 1.3(1)ꢁ. The molecules form a dimer-
like arrangement via an intermolecular p–p interaction.
˚
The C–Hꢀ ꢀ ꢀN interaction (Hꢀ ꢀ ꢀN distance: 2.53 A) con-
structs zig-zag molecular chains along the b-axis.
Considering the intramolecular geometries of these mol-
ecules, the bond lengths within the azole moieties are as
usual and comparable to those observed for N-aryl tetraz-
oles [12,20] and triazoles [21]. The CAzole–CFc or Ph bond
˚
lengths in the ferrocenyl azoles [1.415(2) A in FcTr,
˚
˚
1.421(5) A and 1.4168(17) A in FcTe] were shorter than
˚
those in the ferrocenylphenyl azoles [1.430(4) A and
˚
˚
1.431(4) A in FcPhTr, 1.431(4) A in FcPhTe] and other
N-aryl azoles. The torsion angles between the azole and
adjacent rings vary between 4.8ꢁ and 40.6ꢁ, suggesting that
the torsion angle is susceptible to intermolecular packing
forces.

T. Mochida et al. / Journal of Organometallic Chemistry 691 (2006) 4882–4889
4887
3. Conclusions
by column chromatography (silica gel, chloroform:ace-
tone = 9:1, Rf = 0.29). Yellow powder (57 mg, yield 45%).
1H NMR (CDCl3, ppm): d = 4.26 (s, 5H), 4.28 (t, 2H,
J = 1.8 Hz), 4.56 (t, 2H, J = 1.8 Hz), 8.37 (s, 2H). IR
(KBr, cmꢁ1): 3095, 2924, 1651, 1540, 1411, 1240, 1107,
1054, 874, 805, 644, 491. Mp (DSC) = 182.0 ꢁC. Anal.
Found: C, 56.74; H, 4.41; N, 16.47%. Calc. for
C12H11FeN3: C, 56.95; H, 4.38; N, 16.60%.
Four ferrocene-based triazole and tetrazole ligands have
been prepared by standard methods, although the yields
were found to be lower than those for N-aryl azoles. These
molecules are redox-active ligands that might be useful for
the preparation of multi-functional metal complexes. X-ray
crystallography revealed that weak intermolecular CHꢀ ꢀ ꢀN
hydrogen bonds are formed between the azole moieties in
most cases, which are important to their crystal architec-
tures. In particular, two polymorphs were found for 4-ferr-
ocenyltetrazole, which provides a good example of the
roles of the CHꢀ ꢀ ꢀN interactions and p–p stacking interac-
tions, which were competitive in this case. Preparation of
metal complexes with these molecules is underway.
Method B. A mixture of aminoferrocene (68 mg,
0.338 mmol)
and
1,2-diformylhydrazine
(30.2 mg,
0.343 mmol) was heated at 180 ꢁC for 3 h. After cooling
to room temperature, the reaction mixture was extracted
with chloroform, and the organic layer washed with water.
Insoluble materials were removed by filtration; the organic
layer was separated, dried over magnesium sulfate, and
evaporated. The crude product was purified by column
chromatography (silica gel, chloroform:acetone = 1:1).
The Rf = 0.84 fraction afforded the desired compound
(4 mg, yield 5%). The Rf = 0.21 fraction afforded ferroce-
nylformamide [15] (29 mg, yield 37%).
4. Experimental
4.1. General methods
N,N-Dimethylformazine dihydrochloride [22] and 4-(4-
iodophenyl)-4H-[1,2,4]triazole [23] were synthesized by
following the reported procedures. Ferrocenylaniline was
prepared by an improved method described below. All
the other reagents and solvents were commercially avail-
able. Zinc chloride was dried under vacuum for 2 days at
120 ꢁC prior to use. All reactions were carried out under
a dinitrogen atmosphere. NMR spectra were recorded on
a JEOL JNM-ECL-400 spectrometer. Infrared spectra
were recorded on a JASCO FT-IR 230 spectrometer as
KBr pellets. UV–Vis spectra were recorded on a JASCO
V-570 UV–VIS/NIR spectrometer. Cyclic voltammograms
were recorded with an ALS/chi electrochemical-analyzer
model 600 A. The redox potentials were measured at a scan
rate of 0.1 V sꢁ1, in acetonitrile containing 0.1 mol dmꢁ3
nBu4NClO4 as the supporting electrolyte. An Ag/Ag+ ref-
erence electrode and a platinum working electrode were
used, and the potentials were referenced to a FeCp2=
4.3. Preparation of 4-(4-ferrocenylphenyl)triazole
(FcPhTr)
Method A. N,N-dimethylformamide azine dihydrochlo-
ride (79.0 mg, 0.37 mmol), ferrocenylaniline (102 mg,
0.37 mmol), and p-toluenesulfonic acid (5 mg, 0.03 mmol)
were dissolved in toluene (1 mL), and the solution was
refluxed for 4 h. After cooling to room temperature, the sol-
vent was removed under reduced pressure and the residue
was dissolved in chloroform. The solution was filtered
through a celite plug toremove insoluble materials. The solu-
tion was washed with water, and the organic layer was sepa-
rated, dried over magnesium sulfate, filtered, and
evaporated. The crude product was purified by column chro-
matography (chloroform:acetone = 9:1, Rf = 0.29). Orange
powder (150 mg, yield 81%). 1H NMR (CDCl3, ppm):
d = 4.07 (s, 5H), 4.40 (t, 2H, J = 1.8 Hz), 4.68 (t, 2H,
J = 1.8 Hz), 7.30 (d, 2H, J = 8.4 Hz), 7.61 (d, 2H,
J = 8.8 Hz), 8.48 (s, 2H). 1H NMR (DMSO-d6, ppm):
d = 4.04 (s, 5H), 4.40 (t, 2H, J = 1.8 Hz), 4.89 (t, 2H,
J = 1.8 Hz), 7.61 (d, 2H, J = 8.8 Hz), 7.71 (d, 2H,
J = 8.4 Hz), 9.13 (s, 2H). IR (KBr, cmꢁ1): 3097, 1534,
1512, 1457, 1228, 1080, 997, 886, 844, 822, 646. Mp
(DSC) = 190.3 ꢁC. Anal. Found: C, 65.47; H, 4.73; N,
12.55%. Calc. for C18H15FeN3: C, 65.68; H, 4.59; N, 12.77%.
Method B. A mixture of ferrocenylaniline (24.2 mg,
þ
FeCp2 couple. Melting points were measured by means
of differential scanning calorimetry (DSC) on a TA instru-
ments Q100 calorimeter. TG analysis was performed under
a dinitrogen atmosphere at a heating rate of 10 ꢁC/min on a
Seiko TG/DTA 220U instrument, in the range 25–400 ꢁC.
4.2. Preparation of 4-ferrocenyltriazole (FcTr)
Method A. N,N-dimethylformamide azine dihydrochlo-
ride (114 mg, 0.53 mmol), aminoferrocene (100 mg,
0.50 mmol), and p-toluenesulfonic acid (6.2 mg,
0.036 mmol) were dissolved in toluene (1.2 mL), and the
solution was refluxed for 4 h. After cooling to room tem-
perature, the solvent was removed under reduced pressure,
and the residue dissolved in chloroform. The solution was
filtered through a celite plug to remove insoluble materials.
The solution was washed with water; the organic layer was
separated, dried over magnesium sulfate, and evaporated
under reduced pressure. The crude product was purified
0.0873 mmol)
and
1,2-diformylhydrazine
(6.3 mg,
0.072 mmol) was heated at 180 ꢁC for 3 h. After usual
workup and column chromatography, 4 mg of the desired
compound was obtained (yield 15%). When decahydro-
naphthalene was used as a solvent, the reaction needed p-
toluenesulfonic acid as a catalyst: the reaction mixture
was heated at 180 ꢁC for 1 day, and the yield was 4.2%.
Method C. To a THF solution (5 mL) of ferrocene
(1.013 g, 5.45 mmol) cooled to 0 ꢁC, t-butyllithium (5 mL,
7.25 mmol, 1.24 mol dmꢁ3 n-pentane solution) was added

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T. Mochida et al. / Journal of Organometallic Chemistry 691 (2006) 4882–4889
dropwise, and the solution was stirred for 15 min. A suspen-
sion of zinc chloride (1.2 g, 8.8 mmol) in THF (13 mL) was
added dropwise to this solution and stirred for 30 min. The
solution was allowed to warm to room temperature, and
stirred for a further 1 h. To this solution were added a
THF suspension (6 mL) of dichlorobis(triphenylphos-
phine)palladium(II) (0.2 g, 0.285 mmol) and a THF solu-
tion (15 mL) of 4-(triazole)phenyliodide (1.471 g, 5.43
mmol). The solution was stirred for 2 days at room temper-
ature, and then the reaction was quenched by adding water
(2 mL). After usual workup and column chromatography,
0.680 g of the desired compound was obtained (yield 38%).
dropwise, and the solution was stirred for 30 min at
ꢁ10 ꢁC. A suspension of zinc chloride (2.0 g, 14.7 mmol)
in THF (20 mL) was added dropwise to this solution and
stirred for 30 min. The solution was allowed to warm to
room temperature then stirred for a further 1 h. To this
solution were added dropwise a THF suspension (20 mL)
of dichlorobis(triphenylphosphine)palladium(II) (420 mg,
0.60 mmol) and a THF solution (15 mL) of 4-iodoaniline
(3 g, 13.7 mmol). After stirring the solution for 1 day at
room temperature, an aqueous solution (20 mL) of sodium
hydroxide (2 g), and dichloromethane (50 mL) were added
successively to this solution. The solution was filtered
through celite and evaporated, the residue dissolved in
dichloromethane (500 mL). The solution was washed with
water, dried over magnesium sulfate, passed through a
short plug of alumina, and evaporated under reduced pres-
sure. The crude product was purified by column chroma-
tography (silica gel, hexane:dichloromethane = 1:1). An
analytically pure sample of 4-ferrocenylaniline [15] could
be obtained by recrystallization from chloroform–pentane
(0.95 g, yield 29%).
4.4. Preparation of 4-ferrocenyltetrazole (FcTe)
To a stirred mixture of aminoferrocene (327.7 mg,
0.163 mmol), sodium azide (134.8 mg, 0.209 mmol), and
anhydrous trimethyl orthoformate (1.6 mL), was added gla-
cial acetic acid (0.5 mL), and the solution was heated at
90 ꢁC for 3 h. After cooling to room temperature, the solvent
was removed under reduced pressure. The residue was dis-
solved in chloroform, and the solution was washed with
water. Insoluble materials were removed by filtration, and
the organic layer was separated, dried over magnesium sul-
fate, filtered, and solvent removed under reduced pressure.
The crude material was recrystallized from hexane and fur-
ther purified by vacuum sublimation. Yellow powder
4.7. X-ray crystallographic analysis
Single crystals suitable for X-ray structure analysis were
mostly obtained by slow evaporation of acetone solutions.
The a-form of FcTe was obtained from a methanol solu-
tion while trying to grow a CoCl2 complex. X-ray diffrac-
tion data were collected on a Bruker SMART APEX
CCD diffractometer equipped with a graphite crystal and
incident beam monochromator using MoKa radiation
1
(140.3 mg, yield 56.4%). H NMR (CDCl3, ppm): d = 4.28
(s, 5H), 4.35 (t, 2H, J = 4.2 Hz), 4.82 (t, 2H, J = 1.8 Hz),
8.71 (s, 1H). IR (KBr, cmꢁ1): 3129, 2926, 1636, 1522,
1411, 1209, 1094, 1030, 814, 666, 485. Mp
(DSC) = 165.6 ꢁC. Anal. Found: C, 52.00; H, 4.00; N,
21.93%. Calc. for C11H10FeN4: C, 52.00; H, 3.97; N, 22.05%.
˚
(k = 0.71073 A). The data were corrected for absorption
by using the SADABS program [24]. The structures were
solved by direct methods (SHELXS 97 [25]) and expanded
using Fourier techniques. The non-hydrogen atoms were
refined anisotropically. CCDC-606793 (for FcTr),
-615410 (for FcTe, a-form), -602192 (for FcTe, b-form),
-602193 (for FcPhTr), and -602194 (for FcPhTe) contain
the Supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
4.5. Preparation of 4-(4-ferrocenylphenyl)tetrazole
(FcPhTe)
To
a
mixture of ferrocenylaniline (99.2 mg,
0.358 mmol), sodium azide (29.1 mg, 0.444 mmol), and
anhydrous trimethyl orthoformate (1.0 mL), was added
glacial acetic acid (0.5 mL) under stirring. The solution
was heated at 100 ꢁC for 3 h. After usual workup, the crude
product was purified by column chromatography (silica
gel, chloroform, Rf = 0.16). Orange powder (80 mg, yield
Acknowledgments
1
68%). H NMR (CDCl3, ppm): d = 4.07 (s, 5H), 4.42 (m,
2H, J = 3.7 Hz), 4.71 (m, 2H, J = 3.7 Hz), 7.61 (d, 2H,
J = 8.8 Hz), 7.66 (d, 2H, J = 8.8 Hz), 8.98 (s, 1H). IR
(KBr, cmꢁ1): 3135, 2356, 1606, 1532, 1473, 1211, 1089,
996, 835, 817, 508. Mp (DSC) = 172.5 ꢁC. Anal. Found:
C, 61.64; H, 4.34; N, 16.89%. Calc. for C17H14FeN4: C,
61.84; H, 4.27; N, 16.97%.
We thank Ms. Fumiko Shimizu for DSC and TG mea-
surements and Mr. Masato Tagomori for the preparation
of FcTe (a-form). We also thank Dr. Ryo Horikoshi and
Mr. Koji Hagiwara for the preparation of ferrocenylani-
line. This work was financially supported by a Grant-in-
Aid for Scientific Research (No. 17685003) from JSPS
(Japan Society for the Promotion of Science) and by
‘‘High-Tech Research Center’’ Project 2005–2009 from
MEXT (Ministry of Education, Culture, Sports, Science
and Technology). This work was performed using facili-
ties of the Institute for Solid State Physics, the University
of Tokyo.
4.6. Preparation of ferrocenylaniline
To a THF solution (10 mL) of ferrocene (2.24 g,
12.0 mmol) cooled to ꢁ10 ꢁC was added tert-butyllithium
(16 mL, 25.0 mmol, 1.56 mol dmꢁ3 n-pentane solution)

T. Mochida et al. / Journal of Organometallic Chemistry 691 (2006) 4882–4889
4889
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Appendix A. Supplementary data
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