A Series of Homo- and Heteroleptic Iron(III) Alkoxides as Precursors for Fe2O3

Article abstract of DOI:10.1002/zaac.201700332

A series of bulky iron(III) alkoxides was synthesized by a ligand exchange reaction using [Fe(OtBu)₃]₂ and 2,4-dimethylpentan-3-ol (HOdp). The resulting complexes are dimers, structural details are compared based on single crystal structure analyses. Investigation of the thermal properties shows a decrease of the melting point upon exchange of the tert-butoxy by Odp^– ligands. Thermolysis leads to volatile products and the formation of phase pure hematite.

Full text of DOI:10.1002/zaac.201700332

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201700332
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
A Series of Homo- and Heteroleptic Iron(III) Alkoxides as
Precursors for Fe O3
2
Stefan Dietrich,[a] Anita Finke,[a] Daniel Fuhrmann,[a] and Harald Krautscheid*[a]
Abstract. A series of bulky iron(III) alkoxides was synthesized by a the thermal properties shows a decrease of the melting point upon
–
ligand exchange reaction using [Fe(OtBu)
3 2
] and 2,4-dimethylpentan- exchange of the tert-butoxy by Odp ligands. Thermolysis leads to
3-ol (HOdp). The resulting complexes are dimers, structural details are
volatile products and the formation of phase pure hematite.
compared based on single crystal structure analyses. Investigation of
Introduction
Bradley et al. investigated homoleptic complexes of various
iron(III) alkoxides and the influence of the ligand on physical
properties. It was found that volatility increases with increas-
Iron(III) alkoxides came into focus of research as precursors
for thin film deposition by CVD and ALD processes and for
application in catalysis.
ising catalysts for the polymerization of lactides. Further-
more, iron(III) alkoxides are used as precursors for synthesis
of nano- and micro-particles of defined size and shape.[ Re-
cently an iron(III) alkoxide was used in an ALD process to
generate hematite and magnetite nanotubes.[
[8]
ing steric demand of the ligands. A high vapor pressure is
[1–3]
E.g., iron(III) alkoxides are prom-
substantial for the use as precursors for CVD and ALD pro-
cesses. Thus, we describe a series of new homoleptic and het-
eroleptic iron(III) alkoxides, containing the sterically de-
manding 2,4-dimethylpentan-3-olate ligand and investigate
their thermolysis behavior as well as structural properties.
[4]
5,6]
3]
Iron(III) alkoxides are known for a long time but their syn-
thesis is still challenging due to their structural complexity re- Results and Discussion
sulting from the presence of oxo, alkoxide and alcohol ligands.
To synthesize homo- and heteroleptic iron(III) alkoxides fer-
ric tert-butoxide was applied as suitable starting material. This
alkoxide was synthesized according to literature by reacting
In 1958 Bradley et al. described a reliable synthesis of various
alkoxides starting from ferric chloride and the respective pri-
mary or secondary alcohol. Treatment with ammonia results in
FeCl with KOtBu in THF. Due to the +I effect of the tBu
3
the formation of ammonium chloride and iron(III) alk-
oxide.[7,8]
group the tert-butoxy ligand is more basic than primary or
secondary alkoxides and was used to introduce 2,4-dimeth-
ylpentan-3-ol (HOdp) alkoxide ligands by an acid base reac-
tion with the secondary alcohol as shown in Scheme 1. Its ste-
ric demand is expected to prevent the formation of polynuclear
clusters, in contrast for methoxide or ethoxide; the large alkyl
groups provide solubility in non-polar solvents.
This method is applicable for primary and secondary
alcohols, but not for tertiary alcohols such as tert-butyl
alcohol. An approach to ferric tert-butoxide was provided by
Mathur et al. and Spandl et al., who suggested a salt metathesis
reaction between ferric chloride and sodium tert-butoxide.[1,9]
Adopting this to the reaction of ferric chloride with
sodium methoxide or sodium ethoxide does not lead
to the desired ferric alkoxides Fe(OR) , but to the more
3
complex oxo-alkoxides [Na Fe O(OMe) (HOMe) ] and
2
6
18
6
[10,11]
[
Fe O (OEt) (EtOH)], respectively.
Due to the steric de-
9
3
21
mand of the tert-butyl group, iron tert-butoxide could be iso-
lated as [Fe(OtBu) ] . Spandl et al. used this dimer as starting
3
2
material in a ligand exchange reaction with iron(III) chloride
and were able to isolate the heteroleptic compounds
[
Fe(OtBu)Cl ] and [Fe(OtBu) Cl] with dimeric structures as
2 2 2 2
[9]
well.
Scheme 1. Preparation of the complexes 2–4.
The synthesis of 2 is based on a ligand exchange reaction
by a stoichiometric treatment of 1 with 2,4-dimethylpentan-3-
ol. The product is obtained as green crystalline material in
65% yield. The same procedure was first applied for the syn-
thesis of 3, but the reaction of a stoichiometric amount of 2,4-
dimethylpentan-3-ol with 1 in a 2:1 ratio only results in a mix-
ture of 2 and 3, as confirmed by PXRD. This behavior might
*
Prof. Dr. H. Krautscheid
E-Mail: krautscheid@rz.uni-leipzig.de
[
a] Institut für Anorganische Chemie
Universität Leipzig
Johannisallee 29
04103 Leipzig, Germany
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201700332 or from the au-
thor.
Z. Anorg. Allg. Chem. 2018, 644, 180–185
180
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
be due to the increased steric demand of the 2,4-dimeth-
ylpentan-3-olate ligand. To shift the chemical equilibrium to steric demand, the 2,4-dimethylpentan-3-olate (Odp ) ligand
The crystal structure of 2 is shown in Figure 2. Due to its
–
the desired product, an excess of 2,4-dimethylpentan-3-ol was acts as a terminal and not as a bridging ligand. The same is
–
used. Product 3 could be isolated as green-brown crystalline observed for 3, where all four Odp ligands are in terminal
material in 64% yield despite the steric issues. With respect to positions (Figure 3) while the less sterically demanding tert-
these results, exchanging all tert-butoxy ligands by 2,4-dimeth- butoxy ligands act as μ bridges between the two iron atoms.
2
ylpentan-3-ol seems to be unfeasible. However, a complete ex-
change of all tert-butoxy ligands by 2,4-dimethylpentan-3-ol high steric demand of terminal and bridging Odp ligands cor-
Regarding the structure of the homoleptic complex 4, the
–
was successful by shifting the chemical equilibrium by remov- relates with the challenging synthesis of [Fe(Odp) ] . Its crys-
3
2
ing the tBuOH which is released during the reaction. This was tal structure is shown in Figure 4. The organic residues of the
accomplished by heating the reaction to reflux while distilling μ2-2,4-dimethylpentan-3-olate bridging ligands are orientated
off the produced tBuOH together with toluene. With this almost perpendicular to the Fe···Fe axis. This enables the ter-
method 4 could be isolated as brown crystalline material with minal 2,4-dimethylpentan-3-olate ligands to orientate around
50% yield.
the iron center. In Table 2 selected bond lengths and angles of
–4 are listed. Only small differences in Fe–O bond lengths
1
and O–Fe–O angles could be observed comparing the struc-
tures of 1–4. In contrast to compounds 2 and 3 a slightly longer
Crystal Structure Analyses
From products 2–4 single crystals suitable for crystal struc- Fe···Fe distance is found in 4 due to the higher steric demand
–
ture analysis could be obtained. The basic crystallographic data of the bridging Odp ligand. This also effects the O1–Fe1–O1a
are summarized in Table 1. All three compounds consist of a angle and results in a smaller angle than in 2 and 3. The bond
3
+
dinuclear structure, where the Fe atoms are coordinated by lengths of Fe–O bonds seem to be not effected significantly by
four ligands each in a distorted tetrahedral coordination mode. the organic substituent and are in the range of a typical Fe–O
The dimers contain four terminal and two bridging alkoxide bond.[ The angle O2–Fe1–O3 between the terminal ligands
ligands to form neutral complexes. These structures are similar varies slightly between 114° for 3 and 118° for 2. This angle
to that of ferric tert-butoxide 1. Compounds 2 and 4 crystallize might be mainly caused by the orientation of the ligands and
1]
¯
in the triclinic space group P1 (Z = 1) with an inversion center not only by the type of ligand. The O1–Fe1–O1a angles are in
between the two iron atoms. In contrast, compound 3 crys- the range of 80–82° and are significantly smaller than the ideal
tallizes in the monoclinic space group P2 /c with two formula angle of 109.5° for tetrahedral coordination. This is caused by
1
units per unit cell (Figures S1–S3, Supporting Information). the four-membered ring formed by Fe1–O1–Fe1a–O1a, which
The 2 screw axis along b and the glide plane create two orien- enforces a reduced angle. Both, the steric demand of the li-
1
tations of the centrosymmetric molecule in the unit cell of 3 gands as well as the formation of the four-membered ring lead
as shown in Figure 1.
to a distorted tetrahedral coordination mode.
Table 1. Crystallographic data of [Fe(OtBu)
2
(Odp)]
2
(2), [Fe(OtBu)(Odp)
2
]
2
3 2
(3), and [Fe(Odp) ] (4).
2
3
4
Formula
Fe
2
O
6
C
30
H
66
Fe
2
O
6
C
36
H
78
Fe
2 6 42 90
O C H
Formula mass M /g·mol–1
Temperature T /K
Crystal color and shape
Crystal size /mm
Crystal system
Space group
a /pm
b /pm
c /pm
α / °
β / °
634.52
180(2)
718.68
180(2)
brown block
0.4ϫ0.3ϫ0.1
monoclinic
802.83
213(2)
yellow block
0.3ϫ0.3ϫ0.2
triclinic
brown block
0.3ϫ0.2ϫ0.1
triclinic
¯
¯
P1
P2
1
/c
P1
957.68(4)
1002.54(5)
1068.11(5)
80.549(4)
85.040(4)
67.497(4)
934.25(8)
1
1.128
0.809
2.5–29.0
15525
961.45(5)
1358.59(5)
1679.44(8)
90
101.967(4)
90
2146.0(2)
2
1.112
1055.93(6)
1108.43(7)
1136.55(7)
75.152(5)
82.991(5)
67.095(5)
1184.1(1)
1
1.126
0.651
2.1–25.5
13255
γ / °
6
3
Cell volume V / 10 pm
Z
Density (calcd.), ρ /g·cm–3
Absorption coefficient μ /mm–1
θ range / °
0.712
2.2–26.5
13732
Measured reflections
Independent reflections (Rint
Observed reflections [I Ͼ 2σ(I))
)
4954 (0.0614)
3976
4433 (0.0751)
3344
4121 (0.0683)
2943
Parameters
182
211
238
R
wR
1
(observed reflections)
0.0521
0.1465
0.5 and –0.6
0.0356
0.0894
0.5 and –0.5
0.0446
0.1086
0.6 and –0.2
2
(all data)
Max./min. residual e density / 10 pm–3
–
–6
Z. Anorg. Allg. Chem. 2018, 180–185
www.zaac.wiley-vch.de 181
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Figure 2. Molecular structure of 2; hydrogen and disordered atoms are
omitted for clarity; thermal ellipsoids are drawn at the 50% probability
level.
Figure 3. Molecular structure of 3; hydrogen atoms are omitted; 50%
ellipsoids.
Figure 1. Simplified packing diagrams of 2 (top), 3 (middle), and 4
bottom) with view along [100], only Fe and O atoms are shown.
(
Thermal Properties
The thermal behavior of 2–4 as well as [Fe(OtBu) ] (1) as
3
2
Figure 4. Molecular structure of 4; hydrogen atoms are omitted; 50%
ellipsoids.
a reference compound were investigated by simultaneous ther-
mal analysis (TG-DTA-MS). Based on this analysis the melt-
ing point, the temperature range of thermolysis, and the weight
–
loss were determined. The expected weight loss was calcu- ligands exchanged by Odp . The lowest melting point is ob-
lated, based on the assumption that the thermal decomposition served for the homoleptic complex 4 at 75 °C, 84 K lower than
results in the formation of Fe O as reported by Mathur et al. the melting point of the structurally similar ferric tert-butoxide
2
3
for the thermal decomposition of 1.[ The thermal analysis 1. This effect might be due to the bulky organic groups of the
1]
–
data are summarized in Table 3. Noticeably, the melting point, Odp ligand. The nonpolar alkyl groups shield the polar center
determined as the peak temperature of the endothermic peak of the complex more efficiently and diminish the attractive
in the DTA graph (Figure 5 and Figures S4–S6, Supporting intermolecular forces. This results in a decreasing melting
Information) decreases in the series with the number of OtBu– point with increasing number of Odp ligands.
–
Z. Anorg. Allg. Chem. 2018, 180–185
www.zaac.wiley-vch.de 182
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Table 2. Selected bond lengths /pm and angles /° of complexes 2–4 in comparison to the values of 1.[1] Symmetry operation a: 1–x, 1–y, 1–z.
1
2
3
4
Fe1···Fe1a
Fe1–O1
Fe1–O1a
Fe1–O2
Fe1–O3
O3–Fe1–O2
O1–Fe1–O1a
295
197
178
169
178
113
82
298.90(9)
196.80(5)
196.36(4)
179.65(6)
178.28(8)
117.69(9)
81.02(7)
298.19(5)
196.97(3)
196.78(3)
180.22(6)
178.20(3)
113.82(9)
81.60(7)
303.1(1)
198.42(5)
197.78(5)
180.29(6)
180.60(7)
115.8(1)
80.08(8)
Table 3. Thermal properties of compounds 1–4, obtained from thermo- fied by NMR spectra of the trapped volatile thermolysis prod-
gravimetric analysis in argon atmosphere.
ucts (Figures S12, S13, Supporting Information).
1
2
3
4
The solid residues of the thermal decomposition (TG-DTA
up to 900 °C) of 1–4 were analyzed by PXRD. The diffraction
patterns (Figure 6 and Figures S7–S10, Supporting Infor-
mation) show the phase pure formation of hematite (Fe O )
Melting point /°C
159
108
254
271
74.5
74.8
88
75
Thermolysis onset /°C 235
239
263
72.6
77.8
207
257
80.0
80.1
Thermolysis end /°C
Weightloss exp. /%
Weightloss calcd. /%
248
73.1
71.0
2
3
for the decomposition of all complexes 2–4.
3 2
Figure 5. TG-DTA analysis of [Fe(Odp) ] (4), performed in an argon
–1
atmosphere, heating rate 10 K·min .
Furthermore, the thermolysis reaction of complexes 1–4 was
analyzed by TG-DTA. It is characterized by the final tempera- after thermal treatment of 1–4 up to 900 °C in an argon atmosphere in
Figure 6. X-ray powder diffraction patterns of the residues obtained
ture of decomposition as well as the weight loss. The final comparison to the simulated pattern based on crystal structure data of
[
12]
hematite.
temperature of the decomposition follows a special pattern,
where 1 exhibits the lowest final temperature. The observed
final temperature of 1 is in agreement with the results of
Interestingly, PXRD measurements after thermolysis up to
00, 400, and 500 °C show patterns consistent with the forma-
tion of magnetite, Fe O , or maghemite, γ-Fe O , which can
Mathur et al.[ Exchanging one tert-butoxy ligand by Odp ,
1]
–
3
the final temperature rises to 271 °C and decreases with more
–
3
4
2 3
Odp ligands to 257 °C for complex 4. The weight loss fits
hardly be distinguished by conventional X-ray diffraction
methods.[ As expected, the broad peaks get sharper with
increasing temperature. Between 500 and 600 °C the color of
the solid residue changes from brown-black to red consistent
with the transformation to hematite, α-Fe O , in agreement
with the X-ray diffraction pattern measured after heating to
600, 700, and 800 °C (Figure S14, Supporting Information).
Since TG-MS experiments do not show any signals in the
range above 300 °C and based on the same diffraction patterns
observed for thermolysis under inert and atmospheric condi-
exactly to the calculated values for 2 and 4. The deviation for
13]
3
might be due to partial hydrolysis during sample preparation.
–
2
[1]
While 1 is reported to sublime at 80 °C at 10 Torr, 2–4 are
less volatile.
2
3
The volatile products of the thermal decomposition were an-
alyzed by EI-MS. As volatile products for 1 iso-butene and
tBuOH were found in compliance with results of Mathur.[
2]
For the heteroleptic compounds 2 and 3, in addition to iso-
butene and tBuOH, the release of 2,4-dimethylpentan-3-ol and
2,4-dimethyl-2-pentene was observed originating in the 2,4-
dimethylpentan-3-olate ligand. Accordingly, as volatile prod- tions, the iron oxide phase formed by thermal decomposition
ucts of the decomposition of 4 2,4-dimethylpentan-3-ol and of 1–4 is assigned to maghemite, which is transformed to he-
2,4-dimethyl-2-pentene are formed. These results are also veri- matite at elevated temperatures.
Z. Anorg. Allg. Chem. 2018, 180–185
www.zaac.wiley-vch.de 183
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
2
.0 mmol) was added dropwise. The green solution turned brown
Conclusions
slowly while heating to 90 °C for 2 h. The solvent was evaporated and
The new homo and heteroleptic iron(III) alkoxides the crude product was recrystallized from n-pentane to yield the de-
Fe(OtBu) (Odp)] (2), [Fe(OtBu)(Odp)2]2 (3), and sired product as olive-green crystals (yield 412 mg, 65%).
Fe(Odp) ] (4) were synthesized by a ligand exchange reac-
Fe : calcd. C 56.8, H 10.5%; found: C 56.3, H 10.1%. MS:
m/z = 562: [Fe
488: [Fe (Odp)
106 (m), 1177 (s), 1190 (s), 1354 (m), 1364 (m), 1469 (w), 2870 (m),
[
[
2
2
C
30
H
66
O
6
2
3
2
+
+
2
(Odp)
2
(OtBu)
3
] , m/z = 520: [Fe ] , m/z
2
(Odp)(OtBu)
4
tion starting from ferric tert-butoxide (1) and 2,4-dimeth-
ylpentan-3-ol. Crystal structure analyses confirm the dimeric
structure of the complexes as well as their structural similarity
to ferric tert-butoxide. By exchanging all tert-butoxy ligands
by 2,4-dimethylpentan-3-ol in complex 4 the melting point de-
+
+
=
1
2
2
2
(OtBu)
2
] ; m/z = 446: [Fe (Odp)(OtBu) ] . IR: ν˜ =
2
3
–
1
927 (m), 2966 (s) cm .
2 2
Synthesis of [Fe(OtBu)(Odp) ] (3): A solution of 1 (2.75 g,
creases to 75 °C. The thermal decomposition occurs in one 5.0 mmol) in 50 mL toluene was treated with 2,4-dimetylpentan-3-ol
step and results in formation of Fe O ; after thermal treatment (11.2 mL, 80 mmol, excess). The green solution turned reddish-brown
2
3
(
600 °C) the diffraction pattern corresponds to phase pure he- while heating under reflux for 5 h. After stirring for 12 h at room tem-
perature the solvent was evaporated and the crude product was
matite for all complexes. These results qualify the new
recrystallized from n-pentane. The product was obtained as green-
brown crystalline material (yield 2.3 g, 64%). C36 Fe : calcd.
iron(III) complexes 2–4 as promising precursors for Fe O3
nanoparticles or thin films and – in combination with other
metal compounds – for ternary oxides.
2
H
78
O
6
2
C 60.2, H 10.9%; found: C 59.8, H 10.7%. MS: m/z = 603:
+
+
[
[
1
Fe
Fe
2
(Odp)
(Odp)
3
(OtBu)
(OtBu)
2
] , m/z = 645: [Fe
2
(Odp)
4
(OtBu)] , m/z = 488:
+
2
2
2
] . IR: ν˜ = 1102 (s), 1110 (s), 1175 (m), 1364 (s),
–
1
378 (m), 1471 (m), 2869 (s), 2905 (s), 2960 (s) cm .
Experimental Section
Synthesis of [Fe(Odp)
3 2
] (4): 1 (550 mg, 1.0 mmol) was dissolved in
Materials and Methods: All reactions were carried out under the ex-
clusion of air and moisture using standard Schlenk technique or a
MBRAUN UniLab Glovebox in an nitrogen atmosphere. All solvents
25 mL of toluene and an excess of 2,4-dimetylpentan-3-ol (5 mL) was
added. The reaction mixture turned reddish-brown and was heated to
reflux. While heating, the toluene and tBuOH was distilled off and a
fresh portion of 25 mL toluene was added to the reaction mixture. This
process was repeated and the red crude product was recrystallized from
n-pentane to obtain the desired compound as brown crystals (yield
were dried with sodium and distilled prior to use. Anhydrous FeCl
was purchased from Acros Organcis, KOtBu from Alfa Aesar. 2,4-
Dimethylpentan-3-ol was dried with CaH and distilled prior to use.
3
2
The iron(III) tert-butoxide dimer 1 was synthesized according to the
literature. [1]
400 mg, 50%). C42
90 6 2
H O Fe : calcd. C 62.8, H 11.3%; found: C 61.8,
+
+
H 11.3%. MS: m/z = 688: [Fe
2
(Odp)
5 2 4
] , m/z = 572: [Fe (Odp) ] , m/z
+
Thermogravimetric analysis was performed with a Netzsch STA 449
= 457: [Fe (Odp) ] . IR: ν˜ = 1100 (m), 1380 (m), 2820 (w), 2871 (m),
2958 (s) cm .
2 3
–1
–
1
F1 thermobalance in an argon atmosphere (heating rate 10 K·min )
combined with an Aeolos QMS 403 D mass spectrometer. Elemental
analysis was measured with a Vario El-Heraeus, IR spectra (750–
Supporting Information (see footnote on the first page of this article):
Supporting Information:
–1
4
000 cm ) with a Bruker Tensor27 equipped with ATR attachment,
EI-mass spectra were measured with a Finnigan MAT 8230.
Unit cell diagrams of the crystal structures of 2- 4; TG/DTA analyses;
PXRD analyses of the thermal decomposition products; IR spectra of
Crystal Structure Analyses: Single crystal diffraction data were col-
lected on imaging plate diffractometer systems STOE IPDS-1 and
IPDS-2T equipped with a sealed Mo X-ray tube and a graphite mono-
1- 4; NMR spectra of the volatile thermolysis products of 2; PXRD
patterns of the solid residues after thermolysis at different tempera-
tures.
α
chromator crystal [λ(Mo-K ) = 71.073 pm]. Data processing was car-
[
14]
ried out with STOE X-Area
software including a numerical absorp-
tion correction. The structures were solved by direct methods using
Acknowledgements
[
15]
SHELXS-2014 and refined using SHELXL-2014.
The C atoms of
the disordered alkyl groups in 2 are refined with site occupation factors
of 0.52(1) and 0.48(1), respectively. All non-hydrogen atoms and non-
disordered atoms are refined with anisotropic thermal parameters. The
coordinates of the hydrogen atoms were included on idealized posi-
tions. The structures are visualized using Diamond 3.2k.[16]
We thank J. Bergmann and O. Erhart for TG-DTA-MS measurements
and M. Rossberg for elemental analysis. We gratefully acknowledge
financial support by Universität Leipzig (PbF-1) and ESF. This work
was funded by the European Union and the Free State of Saxony.
Measurements of powder XRD patterns were performed with a STOE Keywords: Iron(III) alkoxide; Precursor; Fe O ; Iron;
2
3
STADI-P diffractometer system equipped with a sealed Cu X-ray tube Crystal structure; Thermolysis
and germanium (111) monochromator crystal [λ(Cu-Kα1
54.060 pm]. Samples of 1–4 were measured in transmission mode in
a
) =
1
capillaries (Hilgenberg, 0.5 mm), thermolysis products were measured
as flat samples on polymer films at room temperature. Data processing References
[
17]
was carried out with STOE WinXPOW.
formed with Bruker TOPAS 5
Rietveld analysis was per-
[
1] S. Mathur, M. Veith, V. Sivakov, H. Shen, V. Huch, U. Hartmann,
H.-B. Gao, Chem. Vap. Deposition 2002, 8, 277.
[
18]
using the fundamental parameter ap-
proach. The crystallographic data of hematite used as reference was
taken from literature.
[
17]
[
2] S. Mathur, V. Sivakov, H. Shen, S. Barth, C. Cavelius, A. Nilsson,
P. Kuhn, Selected Papers, from the 5th International Conference
on Coatings on Glass, Thin Solid Films 2006, 502, 8.
Synthesis of [Fe(OtBu)
2 2
(Odp)] (2): 1 (550 mg, 1.0 mmol) was dis- [3] J. Bachmann, X. Jing, M. Knez, S. Barth, H. Shen, S. Mathur, U.
solved in 20 mL of toluene and 2,4-dimetylpentan-3-ol (0.28 mL,
Gösele, K. Nielsch, J. Am. Chem. Soc. 2007, 129, 9554.
Z. Anorg. Allg. Chem. 2018, 180–185
www.zaac.wiley-vch.de 184
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
[
[
[
[
[
[
[
4] A. B. Biernesser, K. R. Delle Chiaie, J. B. Curley, J. A. Byers, An-
gew. Chem. Int. Ed. 2016, 55, 5251.
5] J.-J. Zhang, Y.-L. Chen, Y.-F. Sun, T. Huang, A.-S. Yu, RSC Adv. [12] E. Wolska, U. Schwertmann, Z. Kristallogr. 1989, 189, 223.
[11] M. Veith, F. Grätz, V. Huch, Eur. J. Inorg. Chem. 2001, 2001,
367.
2
013, 3, 20639.
6] L. Li, X. Wang, Y. Lan, W. Gu, S. Zhang, Ind. Eng. Chem. Res.
013, 52, 9130.
[13] R. M. Cornell, U. Schwertmann, The Iron Oxides – Structure,
Properties, Reactions, Occurrences and Uses, 2nd ed., Wiley-
VCH, Weinheim, 2003.
2
7] D. C. Bradley, R. K. Multani, W. Wardlaw, J. Chem. Soc. 1958, [14] STOE & Cie GmbH, X-Area 1.70, Darmstadt, Germany, 2014.
1
26.
8] D. C. Bradley, R. K. Multani, W. Wardlaw, J. Chem. Soc. 1958,
153.
9] J. Spandl, M. Kusserow, I. Brüdgam, Z. Anorg. Allg. Chem. 2003,
29, 968.
10] K. Hegetschweiler, H. W. Schmalle, H. M. Streit, V. Gramlich, Received: September 1, 2017
H. U. Hund, I. Erni, Inorg. Chem. 1992, 31, 1299. Published online: January 17, 2018
[15] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112.
[16] Klaus Brandenburg, Diamond 3.2k, Bonn, Germany, 2014.
[17] STOE Cie GmbH, WinXPOW 3.0.2.1, Darmstadt, Germany, 2011.
[18] Bruker, TOPAS 5, Karlsruhe, Germany, 2014.
4
6
Z. Anorg. Allg. Chem. 2018, 180–185
www.zaac.wiley-vch.de 185
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim