The crystal structures, molecular spectra and thermal behaviour of carbamoylferrocene and ferrocenecarbonylhydrazide

Article abstract of DOI:10.1016/j.poly.2009.06.034

Carbamoylferrocene (1) and ferrocenecarbonylhydrazide (2) were synthesised by modified literature procedures and studied by a combination of the conventional spectroscopic methods (IR, MS and NMR), X-ray crystallography and thermal analysis. The crystal structures of two new polymorphs of amide 1 and the structure of hydrazide 2 were determined, revealing extensive hydrogen bonding interactions of the polar ferrocene substituents and supportive π?π stacking interactions. Whereas the thermal behaviour of hydrazide 2 was relatively complicated, thermolysis of amide 1 in the presence of air oxygen led to a complete elimination of the organic constituents in a single step under mild conditions affording essentially pure hematite (α-Fe₂O₃). Mo?ssbauer spectra, powder X-ray diffraction and high-resolution transmission electron microscopy indicated the pyrolytic hematite to result in the form of random aggregates of well crystalline nanoparticles.

Full text of DOI:10.1016/j.poly.2009.06.034

Polyhedron 29 (2010) 134–141
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
The crystal structures, molecular spectra and thermal behaviour
of carbamoylferrocene and ferrocenecarbonylhydrazide
a,
a
a
b
*
ˇ
ˇ
ˇ
ˇ ˇ
´
Petr Štepnicka , Ivana Císarová , Daniel Niznansky , Snejana Bakardjieva
a Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, 128 40 Prague, Czech Republic
Institute of Inorganic Chemistry, v.v.i., Academy of Sciences of the Czech Republic, 250 68 Rez near Prague, Czech Republic
b
ˇ
ˇ
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 21 June 2009
Carbamoylferrocene (1) and ferrocenecarbonylhydrazide (2) were synthesised by modified literature pro-
cedures and studied by a combination of the conventional spectroscopic methods (IR, MS and NMR), X-
ray crystallography and thermal analysis. The crystal structures of two new polymorphs of amide 1 and
the structure of hydrazide 2 were determined, revealing extensive hydrogen bonding interactions of the
Keywords:
Ferrocene
polar ferrocene substituents and supportive
of hydrazide 2 was relatively complicated, thermolysis of amide 1 in the presence of air oxygen led to a
p p stacking interactions. Whereas the thermal behaviour
ꢀ ꢀ ꢀ
Carboxamide
Carbonylhydrazide
Crystal structure
Hydrogen bonding
Thermal behaviour
Hematite
complete elimination of the organic constituents in a single step under mild conditions affording essen-
tially pure hematite (a-Fe2O3). Mössbauer spectra, powder X-ray diffraction and high-resolution trans-
mission electron microscopy indicated the pyrolytic hematite to result in the form of random
aggregates of well crystalline nanoparticles.
Ó 2009 Elsevier Ltd. All rights reserved.
Nanoparticles
1. Introduction
2. Results and discussion
Carbamoylferrocene structural units have found use in diverse
chemistry areas ranging from the design of new ligands and elec-
trochemical sensors to redox labelling of biomolecules [1]. This
apparently reflects high chemical stability of the ferrocene carbox-
amide moiety and its structural versatility, the latter resulting from
the possibility of independently changing both the ferrocene unit
and the carbamoyl group (substituents at the amide nitrogen).
With our previous work, we have demonstrated that phoshino-
carboxamides derived from ferrocene phosphinocarboxylic acids
[2] are versatile ligands and catalyst components [3] whilst the
amides bearing substituents capable of forming hydrogen bonds
possess a considerable potential for the construction of self-assem-
bled organometallic networks [4,5]. The latter aspect led us to ex-
plore the structural properties of the archetypal representative,
ferrocene carboxamide FcCONH2 (1; Fc = ferrocenyl), and its re-
lated hydrazide FcCONHNH2 (2). Although the crystal structure of
the former compound has been already reported as a part of a coor-
dination study [6,7], the structural chemistry of 1 and 2 remains
still rather unexplored. During our work, we isolated and structur-
ally characterised two new polymorphs of 1 and determined the
crystal structure of hydrazide 2. The results of the crystallographic
study are discussed along with the spectroscopic (IR, NMR and MS)
and thermal properties of these compounds.
2.1. Synthesis and spectroscopic characterisation
Carbamoylferrocene (1) [8,9] and ferrocenecarbohydrazide (2)
[10] were prepared by the original literature methods from ferro-
cenecarboxylic acid with only minor alterations, mostly during
the isolation steps. The compounds were crystallised from ethyl
acetate-hexane and isolated as analytically pure, orange crystalline
solids.
NMR spectra of 1 and 2 display the resonances characteristic for
the monosubstituted ferrocene moiety together with the signals
due to the NH protons (1H) or the C@O carbon atoms (13C NMR).
The IR spectra of 1 and 2 are relatively complex, the stretching
N–H bands above 3000 cmꢁ1 and the strong amide bands between
ca. 1520–1660 cmꢁ1 being of particular diagnostic value. Despite
the position of these bands is known to depend on the aggregation
state (hydrogen bonding) and be influenced by strong vibrational
coupling, which may be further enhanced due to the electron-
donating conjugated nature of the ferrrocenyl group, in the present
case it corresponds with the spectra of benzamide [11] and ben-
zoylhydrazide [11c] as the organic analogues.
The electron-impact mass spectrum 1 is dominated by the
molecular ion (base peak). This species decomposes predominantly
by elimination of water molecule (possibly thermolysis), by the
loss of (C5H4CONHNH2)ꢀ radical, and by a loss of C5H4CO species,
which is likely to be associated with a transfer of the NH2 group
to iron atom yielding fragment ions at m/z 137 [12]. Fragment ions
* Corresponding author. Fax: +420 221 951 253.
ˇ
ˇ
E-mail address: stepnic@natur.cuni.cz (P. Štepnicka).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.06.034

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P. Štepnicka et al. / Polyhedron 29 (2010) 134–141
135
typical for ferrocene derivatives at m/z 121 ([C5H5Fe]+) and 56 (Fe+)
are also present. It is worth noting that whereas the fragmentation
pattern of 1 only partly parallels the fragmentation of benzamide,
which decomposes predominantly to ions [MꢁNH2]+, [MꢁH2O]+
(thermolysis) and [MꢁCONH2]+ [13,14], the fragmentation of 2+ꢀ
by elimination of NHNH2 a CONHNH2 radicals corresponds well
with the decomposition pathway of [PhCONHNH2]+ꢀ [15]. An addi-
tional intense peak at m/z 129 (relative abundance 56%) in the
mass spectrum of the hydrazide can be tentatively attributed to
[C10H9]+, resulting formally via a loss of (CO + NHNH2 + Fe) from
the molecular ion.
as 1a and 1b), both crystallising with the symmetry of the P21/c
space group. View of the molecule of 1a is shown in Fig. 1. A com-
parison of the molecular geometric parameters for both poly-
morphs is presented in Table 1.
The molecular structures of 1a and 1b are quite similar and per-
fectly match the geometry previously reported [6]. Besides, the
structural parameters of the amide groups in 1a and 1b compare
favourably to those reported for benzamide [16]. Some minor dif-
ferences between the molecules of 1a and 1b can be attributed to
hydrogen bonding interactions. In both cases, the ferrocenyl
groups are eclipsed and display similar Fe-ring centroid distances
and negligible tilts. The amide moieties are rotated by ca. 10° from
their parent cyclopentadienyl planes.
2.2. Description of the crystal structures
The crystal assembly of polymorph 1a resembles that observed
for the monoclinic polymorph (P21/n) characterised previously
(henceforth denoted as 1c) [6]. Likewise 1c, the individual amide
molecules in the structure of 1a associate into discrete hydrogen
bonded dimers around the crystallographic inversion centres
(eight-membered rings, R22(8) in the graph set theory notation
[17]; Fig. 2). Such dimeric motifs are frequently encountered in the
crystal structure of primary amides [5,18] in which they, however,
are typically combined with lateral interactions mediated by the sec-
ond amide hydrogen. The lack of such contacts makes the dimers in
1a more reminiscent of the isolated dimers typically encountered in
the crystals of carboxylic acids except that the Nꢀ ꢀ ꢀO distance
(2.886(2) Å in 1a; Table 2) is considerably longer than the Oꢀ ꢀ ꢀO sep-
aration (cf. the Oꢀ ꢀ ꢀO distance in ferrocenecarboxylic acid dimer:
2.71(1) Å at room temperature [19], and 2.656(2) Å at 175 K [20]).
Additional stabilization of the molecular array in the crystals of 1a
Two polymorphs of 1 have been isolated serendipitously upon
recrystallisation of the amide from ethyl acetate-hexane (denoted
comes from offset
pꢀ ꢀ ꢀp stacking interaction involving substituted
Fig. 1. View of the molecule of ferrocenecarboxamide in the crystal of 1a.
Displacement ellipsoids enclose the 30% probability level.
Table 2
Hydrogen bond parameters for 1a, 1b and 2 [in Å, °].a
D–Hꢀ ꢀ ꢀA
Compound 1a
N–H91ꢀ ꢀ ꢀOi
Dꢀ ꢀ ꢀA
Angle at H
178
Table 1
Selected distances and angles for 1a and 1b [in Å and °].a
2.886(2)
Parameter
1a
1b
Compound 1b
N–H91ꢀ ꢀ ꢀOii
N–H92ꢀ ꢀ ꢀOiii
Fe–Cg1
Fe–Cg2
\Cp1,Cp2
C1–C11
C11–O
C11–N
O–C11–N
\Cp1, {CON}
1.6500(7)
1.6470(7)
0.82(9)
1.483(2)
1.235(2)
1.339(2)
122.5(1)
10.0(2)
1.6501(8)
1.649(1)
2.1(1)
1.491(2)
1.240(2)
1.327(2)
122.7(2)
10.5(2)
2.963(2)
3.020(2)
173
167
Compound 2
N1–H81ꢀ ꢀ ꢀO21
N2–H82ꢀ ꢀ ꢀO21iv
N2–H83ꢀ ꢀ ꢀO1v
N21–H91ꢀ ꢀ ꢀN22vi
N22–H93ꢀ ꢀ ꢀO1iv
2.946(2)
3.155(2)
3.111(2)
2.987(2)
2.946(2)
166
170
159
154
162
a
The ring planes are defined as follows: Cp1 = C(1–5), Cp2 = C(6–10). Cg1 and
Cg2 denote the respective ring centroids. {CON} is the amide plane, comprising
atoms C11, O, and N.
a
D = donor, A = acceptor. Symmetry operations: (i) 1ꢁx, ꢁy, 2ꢁz; (ii) ꢁx, ꢁ1ꢁy,
ꢁz; (iii) x, ꢁ½ꢁy, ½ + z; (iv) 1ꢁx, 2ꢁy, 1ꢁz; (v) ꢁx, 2ꢁy, 1ꢁz; (vi) 2ꢁx, 1ꢁy, 1ꢁz.
Fig. 2. (a) The dimeric repeating unit in the structure of 1a and (b) projection of the molecular assembly onto the crystallographic bc plane. Hydrogen bonds are indicated
with dashed lines.

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P. Štepnicka et al. / Polyhedron 29 (2010) 134–141
136
Fig. 3. Views of the dimeric units in the structures of 1a (a) and 1c (b) along the hydrogen bond plane illustrating different relations of the proximal molecules. Only the
molecules located above and below the (CONH2)2 H-bonded ring are shown for clarity.
Fig. 4. (a) Hydrogen bond interactions in the structure of 1b and (b) section of the hydrogen bonded layers. Hydrogen bonds are indicated with dashed lines. For clarity, the
bulky ferrocenyl moieties were replaced with black boxes in part (b).
cyclopentadienyl rings related by crystallographic inversion opera-
tions (i.e., exactly parallel) at Cg1ꢀ ꢀ ꢀCg1&(1ꢁx, 1ꢁy, 1ꢁz) distance
3.7855(9) Å (ring slippage being ca. 1.6 Å). Similar interactions oper-
ate also in the structure of 1c.
(Fig. 6). The multiplication of the structurally independent units
is probably the consequence of crystal packing forces because the
molecular structures are virtually identical (Table 3). The only
Despite the seeming similarity, the crystal packing of 1a and 1c
are different, the most distinguishing feature being mutual orienta-
tion of adjacent molecules (Fig. 3), which in turn affects the gener-
ation of supportive intermolecular interactions. Thus, whereas the
dimer units in 1c are interconnected by C–Hꢀ ꢀ ꢀO contacts, no such
interactions were detected in the crystal structure of 1a.
The individual molecules in the structure of 1b aggregate into
centrosymmetric cyclic dimers as well though with slightly longer
Oꢀ ꢀ ꢀN distances (Table 2; relative elongation vs. 1a: 3%). In addi-
tion, however, the ‘other’ amide NH protons are bound to carbonyl
oxygens in adjacent molecules related by the crystallographic glide
planes. Each dimer unit is thus connected to four adjacent mole-
cules with the oxygen atoms acting as bifurcated hydrogen bond
acceptors. This results in the formation of infinite twisted two-
dimensional layers the mean planes of which coincide with the
crystallographic bc planes (Figs. 4 and 5). The lateral N–Hꢀ ꢀ ꢀO
hydrogen bonds are longer than the in-dimer ones, the difference
in the Nꢀ ꢀ ꢀO distanced being 2%.
Hydrazide 2 crystallises with the symmetry of the triclinic
space group P1 with two molecules in the asymmetric unit
Fig. 5. Hydrogen bonded layers in the structure of 1b as projected onto the
crystallographic ac plane. Hydrogen bonds are shown as dashed lines.

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P. Štepnicka et al. / Polyhedron 29 (2010) 134–141
137
Fig. 6. (a) Views of the independent molecules in the crystal of 2 showing the atom labelling scheme. Displacement ellipsoids enclose the 30% probability level. (b)
Superposition of these molecules (inverted molecule 2 was fitted onto molecule 1).
Table 3
likely results in the increase of the number of crystallographically
independent moieties. The distribution of the molecules in the lay-
Selected distances and angles for 2 [in Å and °]a
ers allows for the formation of offset in-layer
p p stacking inter-
ꢀ ꢀ ꢀ
Molecule 1
Molecule 2
actions (molecule 2: Cg3ꢀ ꢀ ꢀCg3&(1ꢁx, 1ꢁy, 1ꢁz) = 3.822(1) Å, ring
slippage is ca. 2.0 Å; see Table 3 for the definition of the ring
planes). These layers are oriented parallel to the crystallographic
ab plane and are separated by the bulky, non-polar ferrocenyl
groups (Fig. 7b).
Fe1–Cg1
Fe1–Cg2
\Cp1, Cp2
C1–C11
C11–O1
C11–N1
N1–N2
O1–C11–N1
C11–N1–N2
\Cp1, {CON}
1.6476(8)
1.650(1)
2.2(1)
1.486(2)
1.239(2)
1.343(2)
1.420(2)
122.8(2)
122.5(1)
8.2(2)
Fe2–Cg3
Fe2–Cg4
\Cp3, Cp4
C21–C31
C31–O21
C31–N21
N21–N22
O21–C31–N21
C31–N21–N22
\Cp1, {CON}
1.6443(8)
1.646(1)
2.4(1)
1.474(2)
1.239(2)
1.350(2)
1.415(2)
121.9(1)
122.5(1)
0.6(2)
2.3. Thermoanalytical study and pyrolysis of 1
Thermal behaviour of 1 and 2 was examined by thermogravi-
metry (TG) and by differential thermal analysis (DTA). The corre-
sponding TG/DTA curves are presented in Figs. 8 and 9. Upon
heating under dinitrogen atmosphere, amide 1 first melts without
apparent decomposition (endothermic: onset 168 °C, peak 170 °C;
cf. mp 167–169 °C [8a]) and then undergoes extensive endother-
mic degradation (onset at ca. 215 °C, peak 247 °C). An additional
endothermic peak is seen at 353 °C (onset 352 °C). The minor
weight loss prior to melting (ca. 1%) can be attributed to sublima-
tion, which was detected during bulk pyrolysis, or to liberation of
adsorbed solvents. The mass change during the main decomposi-
tion step is as high as 75%, suggesting a complete elimination of
all ‘organic parts’ (w(Fe) = 24%).
a
The ring planes are defined as follows: Cp1 = C(1–5), Cp2 = C(6–10), Cp3 =
C(21–25), Cp2 = C(26–30). Cgn (n = 1–4) denote the respective ring centroids whilst
{CON} stands for the amide planes {C11,O1,N1} and {C31,O21,N21}, respectively.
notable difference between the independent molecules can be
found in the rotation of the ‘‘amide” moiety {CON} from the plane
of its parent cyclopentadienyl ring; variations in other geometric
parameters are statistically insignificant. Besides, the geometry of
the hydrazide group (C–C(O)NHNH2) is similar that in
PhC(O)NHNH2 [21].
Although the crystal packing of 2 may resemble that of 1b in
that the hydrazide molecules assemble into puckered layers, the
particular aggregation modes are different (Fig. 7 and Table 2)—
also due to the presence of an additional hydrogen bond donor
group (NH) in the molecules of the former compound. Although
the excess of hydrogen bond donors in 2 is partly balanced by
simultaneous formation of bifurcated N–Hꢀ ꢀ ꢀO and conventional
N–Hꢀ ꢀ ꢀN hydrogen bonds (N.B. The latter are not observed in the
structures of 1a and 1b), this still does not ensure the exploitation
of all the available NH protons (H92 remains non-bonded) and very
In contrast, the thermal behaviour of hydrazide is less straight-
forward [22]. The compound melts between 166 °C (onset) and
168 °C (peak), which is higher that the melting point reported in
the literature (159–160 °C [10]). The melting is immediately fol-
lowed by decomposition. First, the compound decomposes in an
endothermic process (onset 188 °C, peak 196 °C,
then in two closely succeeding steps: a thermally neutral process
at ca. 225 °C ( m ꢂ ꢁ15%) and an exothermic one at 255 °C
(DTA: onset 254, peak 255 °C; m ꢂ ꢁ12%). At higher tempera-
D
m ꢂ –19%) and
D
D
Fig. 7. (a) Section of the hydrogen bonded array in the structure of hydrazide 2. For clarity, only the pivotal carbon atoms of the ferrocenyl groups are shown and the
propagation of the assembly is indicated with arrows. [Note: 1A = molecule 1 at (ꢁx, 2ꢁy, 1ꢁz), 1B = molecule 1 at (1 + x, y, z), 1C = molecule 1 at (1ꢁx, 2ꢁy, 1ꢁz), 2A = molecule
2 at (1ꢁx, 2ꢁy, 1ꢁz), 2B = molecule 2 at (2ꢁx, 1ꢁy, 1ꢁz); unlabelled molecules: (x, y, z)]. (b) Projection of the unit cell onto the crystallographic bc plane.

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P. Štepnicka et al. / Polyhedron 29 (2010) 134–141
138
Fig. 8. TG (full line) and DTA curves (broken line) for amide 1.
Fig. 10. Room temperature Mössbauer spectrum of the pyrolysis product
(ꢀ experimental points, – fit). The asterisk indicates a peak due a minor FeIII impurity.
Fig. 9. TG (full line) and DTA curves (broken line) for hydrazide 2.
Fig. 11. Powder X-ray diffraction patterns of the pyrolysis product.
via aggregation of randomly oriented yet well crystalline spherical
domains with the diameter of ca. 30 nm. Lattice fringes observed in
the individual domains were parallel, indicating monocrystalline
nature of the constituting particles, and the fringe spacing of ca.
2.7 Å corresponded to the (1 0 4) lattice plane of hematite. The size
of the monocrystalline regions estimated from HR TEM images was
in accordance with the results calculated from broadening of the X-
ray diffraction peaks and Scherrer equation (31 4 nm).
tures, the sample weight further decreases though without any
notable DTA effect. Since the thermolysis apparently did not reach
completion, the decomposition product was not analysed.
Because the thermoanalytical data of 1 implied complete re-
moval of organic components under relatively mild conditions,
bulk pyrolysis of the amide was studied next. Upon heating to
400 °C without any rigorous exclusion of air oxygen, amide 1
turned to a very fine, bright red–brown solid, analysing as Fe2O3
(Fe: calc. 69.9, found 69.8%). The oxide is formed very likely by
the reaction of finely dispersed iron as the primary decomposition
product with traces of air oxygen.
3. Conclusions
Amide and hydrazide were prepared from ferrocenecarboxylic
acid and characterised by common spectroscopic methods. The
crystal structures of the compounds revealed a delicate synergy
between of the classical directional N–Hꢀ ꢀ ꢀO/N hydrogen bonds
and supportive soft interactions. Isolation of two new polymorphs
of 1 suggests that the resulting crystal arrays are highly variable
(even with preservation of the set of intermolecular contacts)
and may change with crystallisation conditions that are difficult
to asses and control. Whilst studying the thermal behaviour of
the compounds, it was found that the thermolysis of the amide
proceeds with complete elimination of organic constituents under
relatively mild conditions to afford essentially pure nanocrystalline
Mössbauer spectroscopy and powder X-ray diffraction analysis
indicated the pyrolysis product to be essentially pure ferromag-
netic hematite (a-Fe2O3) [23]. The Mössbauer spectrum (Fig. 10)
displayed a sextet with isomer shift 0.37 mm sꢁ1. This value as well
as the quadrupole splitting ꢁ0.21 mm sꢁ1 and magnetic hyperfine
field 51.5 T were in accordance with the parameters reported for a-
Fe2O3. The spectrum further revealed tiny amounts (ca. 1%) of an-
other FeIII compound (isomer shift 0.33 mm sꢁ1, quadrupole split-
ting ca. ꢁ0.22 mm sꢁ1).
The powder X-ray diffraction patterns (Fig. 11) of the pyrolysis
product fully confirmed the formulation, showing only diffractions
attributable to
a-Fe2O3 [23,24], whilst the sharp diffraction peaks
hematite (a-Fe2O3) when performed in the presence of air oxygen.
On the other hand, the thermolysis of the hydrazide proved to be a
stepwise complicated process.
indicated good crystallinity of the material. Accordingly, high-res-
olution transmission electron microscopy (HR TEM; Fig. 12) re-
vealed the hematite to result as irregular conglomerates formed

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P. Štepnicka et al. / Polyhedron 29 (2010) 134–141
139
Fig. 12. HR TEM micrographs of the pyrolysis product (hematite) at three different magnifications. The lattice fringes in the left image correspond to the (1 0 4) plane
(d = 2.70 Å).
for electron microscopy were prepared by dispersing the sample
powder in ethanol (suspension was treated in an ultrasonic bath
for 10 min) and applying a drop of the resulting very dilute suspen-
sion on carbon-coated grids.
4. Experimental
4.1. Materials and methods
The syntheses were performed under an argon atmosphere. Fer-
rocenecarboxylic acid was prepared by the literature method [25].
Methyl ferrocenecarboxylate was obtained by standard diazo-
methane esterification of ferrocenecarboxylic acid and purified
by column chromatography (silica gel, hexane-diethyl ether
1:3 v/v). Dichloromethane was dried over potassium carbonate
and distilled under argon. Dioxane and methanol were distilled un-
der argon.
Melting points were determined on a standard Kofler apparatus.
NMR spectra were measured with a Varian UNITY Inova 400 spec-
trometer (1H, 399.95; 13C, 100.58 MHz) at 298 K. Chemical shifts
(d/ppm) are given relative to an internal tetramethylsilane stan-
dard. In addition to the standard notation of the signal multiplicity,
vt is used to distinguish virtual triplets arising from magnetically
non-equivalent AA0BB0 spin systems of the substituted cyclopenta-
dienyl rings. IR spectra were recorded in Nujol mulls with an FT IR
Nicolet Magna 760 instrument in the range of 400–4000 cmꢁ1. The
electron ionisation (EI) mass spectra were obtained with a ZAB-EQ
instrument (VG Analytical). Thermogravimetric measurements
(thermogravimetry and differential thermal analysis) were per-
formed with a Setaram SETSYS Evolution thermal analyser (condi-
tions: room temperatureꢁ400 °C, scan rate 2 °C minꢁ1, dynamic N2
atmosphere).
4.2. Synthesis of ferrocenecarboxamide (1)
The procedure was modified from Ref. [8]. Oxalyl chloride
(0.2 mL, ca. 2.3 mmol) was added to a suspension of ferrocenecar-
boxylic acid (230 mg, 1.0 mmol) in dry dichloromethane (10 mL).
The solid acid quickly dissolved to give a red solution. After stirring
at room temperature for 1 h, the reaction solution was evaporated
under reduced pressure, leaving dark viscous oil that was immedi-
ately dissolved in dioxane (5 mL). The dioxane solution was treated
with 25% aqueous ammonia (5 mL), whereupon its colour turned
brown. After stirring in a sealed flask overnight, the volatiles were
removed under reduced pressure and the residue was extracted
with hot ethyl acetate (12 mL in two portions). Combined extracts
were filtered and the clear orange filtrate was allowed crystallising
by gas-phase diffusion of hexane over several days. The separated
amide was filtered off, washed with hexane and dried under vac-
uum. Yield of 1: 162 mg (69%), rusty orange crystalline solid.
1H NMR (CDCl3): d 4.23 (s, 5 H, C5H5), 4.39, 4.68 (2 ꢃ vt,
J0 = 2.0 Hz, 2 H, C5H4); 5.54 (br s, 2 H, NH2; position of this signal
may vary upon changing the solvent and temperature). 13C{1H}
NMR (CDCl3): d 68.62 (CH of C5H4), 69.97 (C5H5), 70.90 (CH of
C5H4), 74.48 (Cipso of C5H4), 172.73 (C@O). IR (Nujol):
m
/cmꢁ1
3460 m, 3364 m br, 3179 m br, 1658 vs, 1637 vs, 1608 vs, 1223
w, 1189 w, 1106 s, 1022 m, 1001 m, 910 m, 835 s, 823 s, 790 m,
704 w, 694 w, 642 w br, 608 w, 543 m, 502 s, 483 s. MS (EI): m/z
(relative abundance) 229 (100, M+ꢀ), 211 (17, [MꢁH2O]+), 164 (5,
[MꢁC5H5]+), 137 (32, [MꢁC5H4CO]+), 121 (10, [C5H5Fe]+), 80 (7),
72 (7), 56 (11, Fe+). HR MS (EI) calc. for C11H11NO56Fe (M+):
229.0190. Found: 229.0189.
The pyrolysis product was dissolved in 20% aqueous HCl (pre-
pared from HCl for trace analysis Merck and bidistilled water) at
50 °C. The solution was diluted with water and analysed for iron
with IRIS Intrepid II XPS spectrometer (ICP-EOS) using axial plasma
view and cyclone type nebulizer (operational conditions: plasma
power 1150 W, nebulizer pressure 25.0 psi, auxiliary gas flux
1.0 ml minꢁ1, sample uptake 2.40 ml minꢁ1). The calibration curve
was constructed from four points (0–20 ppm) for the 259.9 nm
line. Quality control was ensured by inserting a QC sample into
the analytical run.
4.3. Synthesis of ferrocenecarbohydrazide (2)
Transmission 57Fe Mössbauer spectra were recorded at room
The procedure was slightly modified (crystallisation) from Ref.
[10]. Hydrazine hydrate (2 mL 80%, excess) was introduced to a
solution of methyl ferrocenecarboxylate (244 mg, 1.0 mmol) in
methanol (4 mL) and the resulting mixture was heated at reflux
for 8 h (formation of dark insoluble decomposition products was
observed). Then, the reaction mixture was diluted with water
(10 mL), partially evaporated under reduced pressure (to 10 mL)
and cooled to +4 °C. The separated solid was filtered off, washed
with little cold water and dried under vacuum. Crude product
was dissolved in warm ethyl acetate (6 mL), the solution was fil-
tered to remove insoluble impurities and crystallised by addition
of hexane (6 mL) and cooling to +4 °C. The separated hydrazide
temperature in constant acceleration mode using a 57Co(Rh)
source. The velocity scale was calibrated with an
a-Fe foil. X-ray
powder diffraction (XRD) studies were performed with an X’pert
Pro (PANalytical) diffractometer operating with Cu Ka1 radiation
(k = 1.5406 Å). Transmission electron micrographs were obtained
with a Jeol JEM 3010 microscope operating at accelerating voltage
of 300 kV (point resolution of 0.17 nm) and equipped with a Gatan
Multiscan CCD camera (model 794.10BP.4, fibre-optically coupled,
1024 ꢃ 1024 pixel resolution), with a phosphor scintillator for
300 keV operation and EDS attached to TEM-INCA x-stream mod-
ule (Oxford; spectrum range 0–20 keV, 2000 channels). Samples

ˇ ˇ
P. Štepnicka et al. / Polyhedron 29 (2010) 134–141
140
was filtered off, washed with hexane and dried under vacuum.
Yield of 2: 105 mg (43%), rusty orange crystalline solid.
4.5. X-ray crystallography
1H NMR (CDCl3): d 4.02 (br s, 2 H, NH2), 4.21 (s, 5 H, C5H5), 4.37,
4.67 (2 ꢃ vt, J0 = 1.9 Hz, 2 H, C5H4); 5.54 (br s, 1 H, NH) (Note: the
positions of the NH/NH2 signals may change with the solvent
and temperature). 13C{1H} NMR (CDCl3): d 67.90 (CH of C5H4),
69.81 (C5H5), 70.57 (CH of C5H4), 73.99 (Cipso of C5H4), 171.81
Crystals used for single-crystal X-ray diffraction analysis were
grown by cooling solutions of the compounds in ethyl acetate-hex-
ane mixtures (1a: orange block, 0.20 ꢃ 0.25 ꢃ 0.30 mm3, 1b: or-
ange needle, 0.12 ꢃ 0.12 ꢃ 0.45 mm3, and 2: orange block,
0.25 ꢃ 0.38 ꢃ 0.55 mm3). Full-set diffraction data ( h
k
l,
(C@O). IR (Nujol):
m
/cmꢁ1 3280 m br, 32230 w, 1645 s, 1615 s,
2h 6 55.0°–55.2°) were collected with a Nonius KappaCCD diffrac-
1525 s, 1317 m, 1310 m, 1220 w, 1203 w, 1106 m, 1042 w, 1021
w, 1001 w, 957 w, 942 w, 821 s, 687 br m, 589 m, 530 m, 507 s,
485 s, 459 m. MS (EI): m/z (relative abundance) 344 (100, M+),
213 (54, [MꢁNHNH2]+), 185 (61, Fc+), 178 (7), 149 (10), 129 (56),
121 (24, [C5H5Fe]+), 97 (7), 95 (9), 83 (10), 69 (15), 56 (30, Fe+).
HR MS (EI) calc. for C11H12N2O56Fe (M+): 244.0299. Found:
244.0296.
tometer equipped with a Cryostream Cooler (Oxford Cryosystems)
using graphite monochromatised Mo Ka radiation (k = 0.71073 Å).
The data were analysed with the HKL program package and cor-
rected for absorption by a numerical method incorporated in the
diffractometer software [26]. The ranges of the transmission fac-
tors are given in Table 4. The crystal of 1b was a non-merohedral
twin with the volume ratio of the two parts 0.719:0.281. Contribu-
tion of the second part was included into the refinement [twin ma-
trix for hkl indices: (1 0 0.620; 0 –1 0; 0 0 1)].
4.4. Bulk thermolysis of 1
The structures were solved by direct methods (SIR97) [27] and
refined by full-matrix least-squares procedure on F2 (SHELXL97) [28].
All non-hydrogen atoms were refined with anisotropic displace-
ment parameters. The nitrogen-bonded hydrogen atoms were
identified on the difference electron density maps and refined iso-
tropically as riding atoms. All other hydrogen atoms were included
in their calculated positions and refined as riding atoms with Ui-
so(H) assigned to a multiple of Ueq(C) of their bonding carbon atom.
Relevant crystallographic data are given in Table 4. Geometric
parameters and structural drawings were obtained by using a re-
cent version of the PLATON program [29].
A sample of amide 1 (100 mg) in a corundum combustion boat
was inserted into a fused silica tube and heated in an oven under a
very slight nitrogen flow. The temperature was increased from
room temperature to 400 °C at 5 °C minꢁ1, kept at this temperature
for 12 h and then allowed to cool return to the ambient tempera-
ture. The resulting material (fine bright red–brown solid, ca.
10 mg) was analysed as pure hematite. Mass balance is unreliable
due to loss of the material by sublimation. The pyrolysis product
dissolved uniformly in 20% aqueous HCl, leaving no detectable
trace of carbon or metal carbides.
Analysis: Fe content calc. for Fe2O3: 69.9. Found: 69.8%. Powder
X-ray diffraction patterns: d (Å) (relative intensity) 3.67 (24), 2.70
(100), 2.51 (74), 2.20 (23), 1.84 (41), 1.69 (50), 1.60 (12), 1.49 (34),
1.45 (34), 1.35 (4), 1.31 (12), 1.26 (6) (the data correspond with
those published for magnetite [24]). Mössbauer spectral parame-
5. Supplementary data
CCDC 727357, 727358 and 727359 contain the supplementary
crystallographic data for 1a, 1b and 2. These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033;
or e-mail: deposit@ccdc.cam.ac.uk.
ters: isomer shift 0.37 mm sꢁ1, quadrupole splitting ꢁ0.21 mm sꢁ1
,
magnetic hyperfine field 51.5 T (at room temperature).
Table 4
Summary of crystallographic data, data collection and structure refinement param-
eters for 1a, 1b, and 2.
Acknowledgements
Compound
1a
1b
2
This work is a part of the research projects supported by the
Ministry of Education, Youth and Sports of the Czech Republic
(projects nos. MSM0021620857 and LC06070).
Formula
C11H11FeNO
229.06
monoclinic
P21/c (no. 14)
150(2)
C11H11FeNO
229.06
monoclinic
P21/c (no. 14)
150(2)
C11H12FeN2O
244.08
triclinic
P–1 (no. 2)
150(2)
M [g molꢁ1
]
Crystal system
Space group
T [K]
References
a [Å]
b [Å]
c [Å]
7.4368(2)
10.7739(2)
11.6098(3)
13.7270(3)
7.0760(2)
10.0250(4)
7.5268(2)
9.7382(2)
13.9820(3)
82.050(2)
89.146(1)
84.083(2)
1009.59(4)
4
1.606
1.464
0.589–0.690
16799
3.3
4640
4236
2.77
3.15, 6.88
0.41, ꢁ0.47
727359
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4
1.640
948.49(5)
4
1.604
ˇ
ˇ
Z
Dcalc [g mLꢁ1
]
ˇ
ˇ
ˇ
ˇ
l
(Mo K
a
) [mmꢁ1
]
1.585
1.550
T-rangea
0.647–0.735
13194
4.1
2123
1980
0.669–0.833
14618
4.7
10365
8944
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
Diffractions total
Rint [%]b
ˇ
ˇ
Unique diffractions
ˇ
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R (observed diffractions) [%]c,d
R, wR (all diffractions) [%]d
2.27
4.84
2.51, 5.82
0.31, ꢁ0.38
727357
5.72, 12.9
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727358
Dq ]
[e Åꢁ3
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Fo
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c
Diffractions with Io > 2
r
(Io).
R
d
2
R =
R
||Fo|ꢁ|Fc||/
R
|Fo|, wR = [
{w(Fo ꢁFc2)2}/
R .
w(Fo2)2]1/2

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P. Štepnicka et al. / Polyhedron 29 (2010) 134–141
141
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