Facile Syntheses of pure Uranium(III) Halides: UF3, UCl3, UBr3, and UI3

Article abstract of DOI:10.1002/zaac.201700402

Herein we describe a convenient lab scale synthesis for pure and solvent-free binary uranium(III) halides UCl₃, UBr₃, and UI₃. This is achieved by the reduction of the respective uranium(IV) halides with elemental silicon in borosilicate ampoules at moderate temperature. The silicon tetrahalides SiX₄ formed as a side product are utilized for the removal of excess starting material via a chemical vapor transport reaction. The syntheses introduced herein avoid the need for pure metallic uranium and are based on uranium(IV) halides synthesized from UO₂ and the respective aluminum halides and purified by chemical vapor transport. These uranium(III) halides are obtained in single crystalline form. A similar reaction yields UF₃ as a microcrystalline powder. However, no beneficial transport reaction occurs with this halide. Also, a higher temperature has to be applied and steel ampoules have to be used. The identities and purity of the products were checked by powder X-ray diffraction as well as IR spectroscopy. The synthesis of UI₃ enabled its crystal structure determination on single crystals for the first time. UI₃ crystallizes in the PuBr₃ structure type with space group type Cmcm and a = 4.3208(9), b = 13.923(3), c = 9.923(2) ?, V = 596.9(2) ?³, and Z = 4 at T = 100 K.

Full text of DOI:10.1002/zaac.201700402

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201700402
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Facile Syntheses of pure Uranium(III) Halides: UF , UCl , UBr ,
3
3
3
and UI3
Stefan S. Rudel,[a,b] H. Lars Deubner,[a,b] Benjamin Scheibe,[a,b] Matthias Conrad,[a,b] and Florian Kraus*[a,b]
Dedicated to Professor Hartmut Bärnighausen on the Occasion of his 85th Birthday
Abstract. Herein we describe a convenient lab scale synthesis for pure
and solvent-free binary uranium(III) halides UCl , UBr , and UI
. This crystalline form. A similar reaction yields UF
cal vapor transport. These uranium(III) halides are obtained in single
as a microcrystalline
3
3
3
3
powder. However, no beneficial transport reaction occurs with this hal-
ide. Also, a higher temperature has to be applied and steel ampoules
have to be used. The identities and purity of the products were checked
by powder X-ray diffraction as well as IR spectroscopy. The synthesis
is achieved by the reduction of the respective uranium(IV) halides with
elemental silicon in borosilicate ampoules at moderate temperature.
The silicon tetrahalides SiX formed as a side product are utilized for
4
the removal of excess starting material via a chemical vapor transport
reaction. The syntheses introduced herein avoid the need for pure
metallic uranium and are based on uranium(IV) halides synthesized
of UI
the first time. UI
3
enabled its crystal structure determination on single crystals for
crystallizes in the PuBr structure type with space
3
3
group type Cmcm and a = 4.3208(9), b = 13.923(3), c = 9.923(2) Å,
from UO
2
and the respective aluminum halides and purified by chemi-
3
V = 596.9(2) Å , and Z = 4 at T = 100 K.
Introduction
The halides of uranium(III) and uranium(IV) are known to
chemists since Péligot synthesized UCl in 1842 and reduced
4
Thanks to the regained popularity of uranium chemistry a
[28]
it with hydrogen to obtain UCl3.
Various methods for their
variety of remarkable compounds has been discovered in re-
syntheses have been discovered over time which are either
more or less sophisticated and still often lead to impure prod-
ucts or use nowadays (at least in the European Union) hardly
cent years.[
1–23]
UI is widely used as a starting material for
3
organometallic uranium chemistry, but usually in the form of
its organic solvent adducts, like [UI (THF) ] and the more
[29]
3
4
accessible materials like uranium metal or UH3.
In our re-
[24,25]
stable [UI (1,4-dioxane)1.5].
For the synthesis of chlor-
3
cently published report, we summarized the most important
methods currently in use for their synthesis and added a novel
ides, [UCl (Py) ] is utilized as a starting material, since a con-
3
4
[26]
venient synthesis is available.
All these compounds have in
method for the preparation of highly pure and solvent-free
common, that their coordinating solvent molecules often can-
not be removed to yield the neat binary halides. In solid state
chemistry, where comparatively harsh, high-temperature con-
ditions are usually applied, decomposition of organic ligands
could lead to the formation of undesired oxides or carbides of
uranium, which will be reported elsewhere. But also for the
investigation of the coordination of weak ligands, the absence
of competing ligands is favorable. A straightforward non solid-
[30]
UCl , UBr , and UI .
But still we found a convenient syn-
4
4
4
thesis for the uranium(III) halides to be lacking. An overview
of common syntheses, properties, and spectroscopic data of
III
[31]
U
compounds is given in a review by J. Dro z˙ d z˙ y n´ ski.
UF is usually produced by the reduction of UF with rigor-
3
4
ously purified hydrogen inside a stainless steel tube. The tem-
perature required for this reaction is rather high (around
000 °C) and side reactions easily occur. The presence of
moisture, oxygen, and oxygen atom containing materials, like
corundum or silica boats, has to be excluded thoroughly, other-
1
state chemical synthesis for neat UI in ethyl ether has been
3
developed, but such UI always contains some percent of un-
3
avoidable organic impurities which may not be desired.[
These could be removed by extraction with THF, which, how-
ever, introduces THF as a ligand.
27]
wise uranium oxides will be formed. Even UF made from
4
UO in a stream of HF usually contains too much moisture for
2
[29]
the preparation of oxide-free UF3.
A suitable reaction for
small scale batches is the reduction of UF with aluminum in
4
*
Prof. Dr. F. Kraus
an inductively heated graphite crucible. At a temperature of
E-mail: florian.kraus@chemie.uni-marburg.de
9
00 °C AlF is formed, which sublimes off the nonvolatile UF
3
[
[
a] Fachbereich Chemie
Philipps-Universität Marburg
Hans-Meerwein-Str. 4
5032 Marburg, Germany
b] WZMW
Hans-Meerwein-Straße
5039 Marburg, Germany
[32]
in the applied high vacuum.
Although much more convenient than the reduction of UF4,
3
the reaction of UCl with hydrogen also requires a special ap-
4
paratus and an exact control of reaction conditions if a com-
plete reaction is to be achieved. At the required temperature of
3
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201700402 or from the au-
thor.
5
00–580 °C, sintering and inclusion of UCl easily occurs in
4
[29,33]
the formed UCl3.
Z. Anorg. Allg. Chem. 0000, ᭿,0–0
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The reduction of UBr with hydrogen again requires a high silicate glass, but also fused silica, proved to be unsuitable for
4
temperature of 700 °C for complete reaction and leads to the this synthesis. These glasses either melt or are heavily attacked
formation of side products: Either oxide contamination or re- by hot uranium fluorides. Even complete conversion to UO2
duction to products of lower bromide content occurs.[
29]
was observed in some cases. We also tried using nickel and
Alternatively to the reduction of the uranium(IV) halides, platinum ampoules, which led to incomplete reduction, proba-
UCl and UBr are conveniently formed by reaction of UH
bly due to the formation of silicides. Steel (316L, 1.4435)
with HCl or HBr, respectively, but this requires the availability proved to be a cheap and well suitable material.
3
3
3
of pure uranium metal for the preparation of the highly pyro-
Like the aluminum halides, the silicon halides appear to act
as transport agents for the uranium tetrahalides. The allegedly
formed gas phase complexes seem to induce very smooth reac-
phoric UH , as well as the purification of the applied gases
3
[
29]
and thus a rather complex apparatus.
UI3 is synthesized by passing a stream of iodine over
uranium metal at a pressure of ca. 10 mbar inside a furnace
with four different temperature zones.[ If UI is available,
tions, because the reduction of UX (X = Cl, Br, I) with Si
4
–
5
actually changes from a solid-solid reaction in the beginning
29]
4
into a solid-gas reaction. Thus, even large crystals of UX of
4
UI should be easily produced by heating the UI in a vacuum
3
4
several millimeters edge length were completely converted
or in a dry stream of inert gas. However, we found this method
to be less suitable than expected.
Regarding uranium(III) halides, only the purification of
into the also crystalline reduction products UX (Figure 1).
3
Furthermore, the reaction offers the opportunity to apply an
excess of UX , which, after the reaction is completed, can be
4
UCl by chemical vapor transport with iodine has been re-
3
removed by placing the ampoule into a temperature gradient.
ported.[ No other purification processes for uranium(III) hal-
ides have been established to the best of our knowledge. Start-
ing their syntheses from pure starting materials is thus essential
as nonvolatile impurities often cannot be removed. Based on
our report on the synthesis of the pure uranium(IV) halides
29]
The excess UX is then transported out of the reaction zone
4
and can easily be recovered. This measure ensures the com-
plete reaction of the added silicon, as otherwise, weighing er-
rors could lead to an irremovable silicon impurity in the prod-
ucts.
[30]
UCl , UBr , and UI ,
we present herein a route to the
4
4
4
uranium(III) halides utilizing these tetrahalides as starting ma-
terials and using an ampoule technique that practically ex-
cludes the introduction of impurities.
Results and Discussion
It is known that various metals are capable of reducing Figure 1. From left to right: photos of UF
3 3
, black UCl , dark-brown
UBr , and black UI , synthesized by reduction of the tetrahalides with
uranium(IV).[29,31]
However, the alkali metals, calcium, mag-
3
3
IV
3
silicon. Alexandrite effect of UF with green color under daylight or
a white LED (left) and purple color under fluorescent light (right).
nesium as well as aluminum were reported to fully reduce U
halides to uranium metal.[
29]
Also, in most cases, the
byproducts are hardly removable. Metals forming volatile hal-
ides are more suitable. An example for such a metal is hot
zinc, which was reported to reduce UCl vapors to UCl upon
We did not observe any chemical vapor transport with UF
4
3
3
contact, releasing volatile ZnCl2.[
29,31]
We opted for silicon, as and SiF
it is cheap and available in very high purity. It is well known in the exact stoichiometric ratio and the impurities described
to form volatile or easily sublimeable halides (subl.p.: SiF : above cannot be removed. However, SiF is a gas at room
SiI4: temperature, so the removal of this byproduct is much easier
. Therefore, the starting materials have to be present
4
4
4
[
34]
[35]
[35]
–
2
95.0 °C,
b.p. SiCl : 57.1 °C,
SiBr : 154.7 °C,
4
4
87.5 °C[ ). SiI was reported to decompose to the elements than that of AlF in the reduction with aluminum.
36]
[32]
4
Albeit,
[37]
upon heating under vacuum.
Under the conditions applied silicon will not melt under the applied conditions, which im-
here, we did not observe this reaction. In fact, SiI presumably plies mixing problems that may lead to incomplete reactions
4
only decomposes partially to Si I , which can be sublimed at due to limited diffusion in the solid state. We also tried to
2
6
3
50 °C in a vacuum without further decomposition and it only
reduce β-UF to UF using silicon. Although this reaction is
possible in principle, the results were not reproducible.
5
3
[36]
decomposes to the elements if it is melted.
With the exception of UF , silicon is able to reduce
4
Between 150 and 190 °C UF disproportionates in a vacuum
5
III
uranium(IV) halides to the respective U halides at moderate
to UF6 and black uranium(IV/V) fluorides, and to UF4 at
temperatures of 350 to 450 °C according to Equation (1). This
low temperature allows for the use of easy-to-handle borosili-
cate glass ampoules.
80 °C.[38] The reactivity of UF restricts the choice of am-
2
6
poule materials such that we were not able to find a suitable
material for the handling of UF and silicon at the same time.
6
Thus, side reactions occurred with the ampoules.
4
UX
4
+ Si Ǟ 4 UX
3
+ SiX
4
(X = F, Cl, Br, I)
(1)
Powder X-ray diffraction analyses show good crystallinity
UF also can be reduced by silicon [Equation (1)], however of the products as well as the absence of crystalline impurities
4
higher temperatures are needed (700–800 °C). Naturally, boro- like the starting materials or the oxides, except for the case of
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UF , where a slight impurity of UF was detected (Figure 2,
3
4
Figure 3, Figure 4, and Figure 5). Le Bail fitting resulted in the
refined cell parameters listed in Table 1. Due to the strong
X-ray absorption of the samples, capillaries had to be only
loosely filled to obtain a powder X-ray diffraction pattern.
However, the intensity of the reflections is still reduced, so the
amorphous contribution of the glass capillaries is somewhat
overrepresented in the diffraction experiment. This is avoided
by dilution of the sample with diamond powder, which, never-
3
Figure 4. Powder X-ray diffraction pattern of UBr with Le Bail fit-
ting. The calculated reflection positions are represented by lines below
[
41]
the observed and calculated powder pattern.
The difference curve
is plotted underneath. Profile R factors: R
p
= 2.73%, wR = 3.58%,
p
GOF = 1.87.
Figure 2. Powder X-ray diffraction pattern of UF
considering a UF impurity. The calculated reflection positions are
represented by lines below the observed and calculated powder
3
with Le Bail fitting,
4
pattern.[
tors: R
39,43]
The difference curve is plotted underneath. Profile R fac-
= 2.41%, wR = 3.7%, GOF = 2.11.
p
p
Figure 5. Powder X-ray diffraction pattern of UI
3
with Le Bail fitting.
The calculated reflection positions are represented by lines below the
[
42]
observed and calculated powder pattern.
plotted underneath. Profile R factors: R = 1.85%, wR
1.51.
The difference curve is
p
p
= 2.62%, GOF
=
theless, leads to other problems, like overlapping reflections
(Figure S1, Supporting Information).
Nevertheless, some of the ATR-IR spectra (Figure S2,
Supporting Information) show a minor bump at around
–
1
1
080 cm , which could be attributed to the Si–O stretching
[44]
band.
This might derive from small amounts of adsorbed
Figure 3. Powder X-ray diffraction pattern of UCl
3
with Le Bail fit-
SiO from the hydrolysis of the formed silicon halides.
Probably due to the fragile nature of the lath-like single
2
ting. The calculated reflection positions are represented by lines below
[
40]
the observed and calculated powder pattern.
The difference curve
crystals of UI , no crystal structure based on single crystals
is plotted underneath. Profile R factors: R
p
= 2.35%, wR = 3.19%,
p
3
GOF = 1.46.
has been reported till now. Two powder neutron diffraction
Table 1. Cell parameters of the uranium(III) halides at room temperature.
This work
UF
3
UCl
hP8
3
UBr
hP8
3
UI
3
Pearson Symbol
hP24
oC16
a /Å
b /Å
c /Å
7.18593(6)
7.44382(3)
7.94448(3)
4.3339(2)
13.9996(5)
9.9993(3)
7.35284(8)
4.32298(2)
4.44382(3)
Reference
UF
3
[39]
UCl
3
[40]
UBr
3
[41]
3
UI [42]
a /Å
b /Å
c /Å
7.179
7.345
7.4439(3)
4.3243(3)
7.942(2)
4.441(2)
4.334(6)
14.024(18)
10.013(13)
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Table 2. Reported cell parameters of UI
T /K Type
93 Powder
3
.
a /Å
b /Å
c /Å
Source
2
4.328(5)
4.334(6)
4.324(6)
4.3339(2)
4.3208(9)
14.011(16)
14.024(18)
13.933(18)
13.9996(5)
13.923(3)
10.005(11)
10.013(13)
9.942(13)
9.9993(3)
9.923(2)
[45]
[42]
[42]
this work
this work
293
Powder
4
2
1
.2
93
00
Powder
Powder
Single crystal
structure analyses on UI have been published so far, both de-
Due to the additional U–I contacts, the trigonal prism around
3
scribing the UI crystal structure as the PuBr structure type the uranium atom is actually bicapped over two of its rectangu-
3
3
with the space group type Cmcm. The sample investigated in lar faces with atomic distances U–I1 = 3.1447(7) Å and U–I2
the first report contained some UO impurity that decreased = 3.2449(6) Å for the atoms forming the prism and U–I2 =
2
the data quality as overlapping reflections had to be dis- 3.4048(8) Å for the capping atoms (Figure 6). The atomic dis-
carded.[ In the second study, a single-crystalline region was tances are in good accordance to the reported ones (Table 3).
used for the determination of the starting structure model
45]
which was refined against powder neutron data.[ Crystals
42]
grown via the synthesis presented here were of such quality
that we were able to determine the crystal structure via single-
crystal X-ray diffraction and gain more precise structural data.
We confirm that UI crystallizes in the orthorhombic PuBr3
3
structure type with space group type Cmcm and a = 4.3208(9),
3
b = 13.923(3), c = 9.923(2) Å, V = 596.9(2) Å , and Z = 4 at
T = 100 K, which is consistent with previously reported values
Table 2).[
42,45]
Crystallographic data is listed in Table 4. How-
(
ever it seems noteworthy, that the inspection of the reciprocal
layer (h0l), calculated from the raw data, revealed several
weak reflections violating the extinction condition for the c-
glide operation (Figure S3, Supporting Information). Ten of
these reflections have a relative intensity I / σ(I ) Ͼ 3. Based
o
o
on the comparison of the ratios Ih0l / I2h0l for several reflec-
tions, we can exclude that they arise from a λ/2 contribution
of the Mo-K radiation. Therefore, we refined the obtained
α
structural model in the four maximal subgroups of Cmcm con-
taining no c-glide plane, namely Amm2, C222 , C2/m, and
1
P2 /m. In all cases however, no improvement of the R-values
1
relative to those obtained for the refinement in space group
Cmcm was observed. Moreover, in all cases, shifts less than
1
pm were enough to restore the Cmcm symmetry.
The crystal structure contains three crystallographic inde-
pendent atoms. The atoms U and I1 are situated on the 4c
position with site symmetry m2m. Atom I2 is located on posi-
tion 8f (site symmetry m.).
The structure can be assembled from distorted trigonal UI6
prisms [I2–I2: 3.6792(10) and I1–I2: 4.2752(11) Å], which are
condensed via their triangular faces, forming columns running
parallel to the a axis. Slabs according to the Niggli formula
2
[UI12/2I26/3] are formed by connection of these columns
ϱ
parallel to (010) through additional U–I contacts. Neighboring
columns are mapped onto each other by the twofold screw axis
parallel to the a axis running through x, ¼, 0. Thus, neigh-
boring columns are shifted by x = ½ relative to each other.
3
The resulting slabs consist of a central layer of uranium atoms Figure 6. Crystal structure of UI . Top: Surrounding of the U atom.
Bottom: Projection along the a axis. Displacement ellipsoids are shown
at a 95% probability level at 100 K. Symmetry operations for
generating equivalent atoms: #1: x + 1, y, z; #2: –x, y, –z + 1/2;
covered on both sides by slightly corrugated layers of iodine
atoms. While the uranium layers have the topology of a 3 net,
6
the iodine layers are composed of rectangles and triangles with
#3: –x + 1/2, –y + 1/2, z – 1/2; #4: –x – 1/2, –y + 1/2, z – 1/2;
6
3
2
I1 lying on a 3 vertex and I2 on a 3 .4 vertex.
#5: x – 1/2, –y + 1/2, –z + 1; #6: x + 1/2, –y + 1/2, –z + 1.
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3
Table 3. Reported atomic distances in UI .
Distance /Å
4.2 K[42]
100 K (this work)
293 K[42]
3.147(10)
293 K[45]
3.165(12)
U–I1 (2ϫ)
U–I1 (1ϫ)
U–I2 (4ϫ)
U–I2 (2ϫ)
I2–I2
3.189(10)
3.1447(7)
4.6765(13)
3.2449(6)
3.4048(8)
3.6792(10)
4.3208(9)
3.254(7)
3.417(8)
3.689(10)
4.324(6)
3.265(7)
3.454(7)
3.713(9)
4.334(6)
3.244(8)
3.456(11)
3.679(18)
4.328(5)
U–U
2
The [UI12/2I26/3] slabs are stacked such that the I1 atoms ampoule and prevented mixing of byproduct in the sink with product
ϱ
in the source. The ampoules were filled with a long funnel in a
glovebox, to prevent soiling the sink as well as the sealing constraint
with nonvolatile substances.
are situated above the rectangular face of a UI prism in the
neighboring slab. With 4.6765(13) Å however, the distance is
too long to be regarded as a bond.
6
The shortest I–I contacts between two layers correspond
Preparation of UF
3
: A steel ampoule was charged with finely ground
with 4.2043(9) Å to the sum of the van der Waals radii of I
UF (100 mg, 0.318 mmol) and powdered Si (2.24 mg, 0.080 mmol),
4
atoms (4.2 Å).[
46]
crimped and welded in an argon atmosphere (ca. 900 mbar). The mix-
ture was heated to 700 °C for 7 d. The yield was quantitative with
respect to silicon.
Conclusions
Preparation of UCl
UCl4 (1000 mg, 2.633 mmol, 20 mg excess) and Si (18.12 mg,
3
: An ampoule was charged with finely ground
Pure and crystalline uranium(III) halides, UX (X = Cl, Br,
I) were prepared by reduction of the respective uranium(IV) 0.645 mmol) and flame sealed under vacuum (1ϫ10 mbar). The
3
–
3
halides with elemental silicon inside borosilicate glass am- starting materials were reacted at 450 °C for 20 d before the transport
poules. Excessive UX was removed in situ from the products reaction was conducted with a source temperature of 350 °C and a sink
4
temperature of 250 °C, to remove the excess of UCl
quantitative with respect to silicon.
4
. The yield was
via a chemical vapor transport reaction with the formed silicon
halide. Using steel ampoules and a higher temperature, UF3
was synthesized in a similar manner, yet without the benefit
of an in situ purification.
Preparation of UBr
UBr (1000 mg, 1.793 mmol, 20 mg excess) and Si (12.34 mg,
0.440 mmol) and flame sealed under vacuum (1ϫ10 mbar). The
3
: An ampoule was charged with finely ground
4
The crystal structure of UI was determined using single-
–3
3
crystal X-ray diffraction for the first time and more precise starting materials were reacted at 400 °C for 14 d before the transport
structural data was gathered. The PuBr structure type was reaction was conducted with a source temperature of 350 °C and a sink
3
confirmed for this compound.
temperature of 230 °C, to remove the excess of UBr
quantitative with respect to silicon.
4
. The yield was
Preparation of UI
1000 mg, 1.341 mmol, 20 mg excess) and Si (9.23 mg, 0.329 mmol)
and flame sealed under vacuum (1ϫ10–3 mbar). The starting materials
3 4
: An ampoule was charged with finely ground UI
Experimental Section
(
All work was carried out excluding humidity and air in an atmosphere
of dried and purified argon (5.0, Westfalen AG) using high-vacuum were reacted at 450 °C for 7 d before the transport reaction was con-
glass lines or a glovebox (MBraun). UF was synthesized by reduction ducted with a source temperature of 450 °C and a sink temperature of
of UF with sulfur in anhydrous HF. UCl
sized by metathesis of UO and the respective aluminum halide and
purified by in situ chemical vapor transport.
4
6
4
, UBr
4
, and UI
4
were synthe-
300 °C. The yield was quantitative with respect to silicon.
2
[
30]
Silicon (Alfa Aesar
Powder X-ray Diffraction: Powder X-ray diffraction was conducted
–
100 mesh 99.9%) was used as supplied. All glass vessels were made with a STOE StadiMP powder diffractometer using Cu-Kα1 radiation,
of borosilicate glass and flame-dried under vacuum before use.
a Ge monochromator, and a Mythen1K detector. Samples were pow-
dered in agate mortars in a glovebox and filled into borosilicate-glass
capillaries, which were flame-dried in vacuo before use.
UF was synthesized in steel ampoules. An 8 cm piece of 3/8th inch
3
steel tube (316L / 1.4435) was crimped in a vise on one side and TIG-
welded. The other side was tapered to 8° on the inside, to facilitate
crimping the ampoule tightly with a vise in a glovebox after inserting
the starting materials. The steel ampoules were heated in a vacuum
inside a fused silica tube.
[
47]
Phase analysis was carried out with WinXPOW,
database.
using the ICDD
[49]
[
48]
Le Bail fitting was done with JANA 2006.
Single Crystal X-ray Diffraction: Single crystals were selected under
exclusion of air in cooled perfluorinated polyether (Galden, Solvay
For the synthesis of UCl
to those used for the synthesis of the uranium(IV) halides.
should be such that a consistent temperature is achieved over the whole Mo-K
length during the reaction and that after the reaction a temperature were reduced with the X-Area software package, scaled with the Laue
3 3 3
, UBr , and UI , we used ampoules similar Solexis) and mounted using the MiTeGen MicroLoop system. X-ray
[
30]
The size diffraction data were collected using the graphite monochromated
radiation of a Stoe IPDS2T diffractometer. The diffraction data
α
[
50]
gradient can be applied for the chemical vapor transport. Ampoules of
about 100 mm length, 19 mm outer diameter, and 1.3 mm wall thick-
ness suited our tubular furnaces. These ampoules were equipped with
a NS14 ground joint for flame drying and sealing. A constriction in
Analyzer and corrected for absorption numerically using X-Red and
[
51–53]
X-Shape.
The structure was solved using Direct Methods
2
(SHELXS-97) and refined against F (SHELXL-2016/6) using the
ShelXle software package.
[
54–56]
Atoms were refined anisotropically.
[
57]
the middle of the ampoule was used for facilitated breakup of the Reciprocal layers were calculated with the program BuildSpace and
Z. Anorg. Allg. Chem. 0000, 0–0
www.zaac.wiley-vch.de
5
© 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
plotted with ViewSpace[58] implemented in the Xarea software pack-
age. Crystallographic data and structure refinement results are summa-
rized in Table 4.
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Table 4. Crystallographic data and refinement results for UI
3
.
UI
3
Color and appearance
black laths
Cmcm (no. 63)
orthorhombic;
4.3208(9)
13.923(3)
9.923(2)
Space group
Crystal system
a /Å
b /Å
4577.
c /Å
[
[
[
11] M. R. MacDonald, M. E. Fieser, J. E. Bates, J. W. Zillner, F. Fur-
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V /Å3
596.9(2)
Z
4
λ /Å
0.71073
T /K
μ(Mo-K
100(2)
42.544
) /mm–1
α
R
int; R
σ
0.112; 0.048
0.039; 0.039
0.090; 0.090
1.188
R(F) [I Ն 2σ (I); all]
wR(F ) [I Ն 2σ (I); all]
S (all data)
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662; 16; 0
5.405; –5.954
Δρmax; Δρmin /e·Å–3
2
014.
Further details of the crystal structure investigations may be obtained
from the Fachinformationszentrum Karlsruhe, 76344 Eggenstein-
Leopoldshafen, Germany (Fax: +49-7247-808-666; E-Mail:
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IR Spectroscopy: IR spectra were recorded with a Bruker alpha FT-
IR spectrometer using the Diamond ATR unit with a resolution of
[
–
1
4
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[59]
ware package.
5
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a mixture of uranium triiodide and diamond powder as well as the IR
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[
[
[
[
[
(h0l) plane of uranium(III) iodide is depicted which shows the men-
tioned systematic absence violations.
Acknowledgements
F.K. thanks the Deutsche Forschungsgemeinschaft for his Heisenberg
professorship and funding. We thank Dr. Harms, X-ray facilities Mar-
burg, for measurement time.
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Keywords: Halides; Uranium; Solid state; Synthesis; Trans-
port reaction
[
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Received: November 3, 2017
Published online: ᭿
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© 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
S. S. Rudel, H. L. Deubner, B. Scheibe, M. Conrad,
F. Kraus* ........................................................................... 1–8
Facile Syntheses of pure Uranium(III) Halides: UF , UCl ,
3
3
UBr , and UI
3
3
Z. Anorg. Allg. Chem. 0000, 0–0
www.zaac.wiley-vch.de
8
© 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim