Facile routes to ThIV, UIV, and NpIV phosphites and phosphates

Article abstract of DOI:10.1002/ejic.201100464

Three actinide(IV) phosphites and a Np^IV phosphate, An ^IV(HPO₃)₂(H₂O)₂ (An = Th, U, Np) and Cs[Np(H_1.5PO₄)(PO₄)]₂, respectively, were synthesized using mild hydrothermal conditions. The first three phases are isotypic and were obtained using similar reaction conditions. Cs[Np(H_1.5PO₄)(PO₄)]₂ was synthesized using an analogous method to that of Np(HPO₃) ₂(H₂O)₂. However, this fourth phase is quite different in comparison to the other phases in both composition and structure. The structure of Cs[Np(H_1.5PO₄)(PO₄)] ₂ is constructed from double layers of neptunium(IV) phosphate with caesium cations in the interlayer region. In contrast, An(HPO₃) ₂(H₂O)₂ (An = Th, U, Np) form dense 3D networks. The actinide contraction is detected in variety of metrics obtained from single-crystal X-ray diffraction data. Changes in the oxidation state of the neptunium starting materials yield different products.

Full text of DOI:10.1002/ejic.201100464

FULL PAPER
DOI: 10.1002/ejic.201100464
Facile Routes to ThIV, UIV, and NpIV Phosphites and Phosphates
Eric M. Villa,[a] Shuao Wang,[a] Evgeny V. Alekseev,*[a,b,c] Wulf Depmeier,[b] and
Thomas E. Albrecht-Schmitt*[a]
Keywords: Radiochemistry / Actinides / Hydrothermal synthesis / Neptunium / Uranium / Thorium
Three actinide(IV) phosphites and
a
NpIV phosphate,
and structure. The structure of Cs[Np(H1.5PO4)(PO4)]2 is con-
structed from double layers of neptunium(IV) phosphate with
caesium cations in the interlayer region. In contrast,
An(HPO3)2(H2O)2 (An = Th, U, Np) form dense 3D networks.
The actinide contraction is detected in variety of metrics ob-
tained from single-crystal X-ray diffraction data. Changes in
the oxidation state of the neptunium starting materials yield
different products.
AnIV(HPO3)2(H2O)2 (An = Th, U, Np) and Cs[Np(H1.5PO4)-
(PO4)]2, respectively, were synthesized using mild hydrother-
mal conditions. The first three phases are isotypic and were
obtained using similar reaction conditions. Cs[Np(H1.5PO4)-
(PO4)]2 was synthesized using an analogous method to that
of Np(HPO3)2(H2O)2. However, this fourth phase is quite dif-
ferent in comparison to the other phases in both composition
A similar, yet relatively unexplored, area of actinide
chemistry is that of actinide phosphites. Although phos-
phate and phosphite exhibit somewhat similar geometries
and bond lengths, the removal of one oxygen atom provides
a unique opportunity for new coordination chemistry. To
date few actinide phosphites have been synthesized, and
most make use of organic templates.[23–28] Actinide phos-
phite chemistry is also of interest because comparisons can
be made with the solid state chemistry of other actinide
oxoanion systems that contain C3v anions, including selen-
ite,[29] tellurite,[30] and iodate.[31] Phosphite is also a C3v
anion, and here the lone pair found on the aforementioned
anions has been replaced by a hydrogen atom. However, the
chemistry of phosphite is expected to be markedly different
from that of anions such as selenite or iodate, because these
anions are mild to strong oxidants, and phosphite is a
strong reductant. Therefore, one would expect phosphite to
stabilize the tetravalent oxidation state, whereas selenite and
iodate generally yield penta- or hexavalent oxidation states.
Herein we provide data that supports these suppositions
with a series of isotypic thorium(IV), uranium(IV), and
neptunium(IV) phosphites, with general formula
AnIV(HPO3)2(H2O)2 (AnIV = Th, U, Np), and a new caes-
ium neptunium(IV) phosphate, Cs[NpIV(H1.5PO4)(PO4)]2.
Introduction
The limited solubility of actinide phosphates, such as
uranyl phosphates, plays an important role in our under-
standing of how actinides migrate through the environment,
be it from a natural deposit or from a geological repository
for nuclear waste. Specifically, the fate of 237Np is of con-
cern in these repositories owing to its long half life of
2.14ϫ106 years, and the fact that its amount actually in-
creases in the short term owing to the α decay of 241Am,
which is also present in used nuclear fuel. 237Np is responsi-
ble for most of the long term radioactivity from a reposi-
tory if actinides are not removed from the fuel.[1]
Initial studies of the fundamental properties of neptu-
nium phosphates have been preformed to better design acti-
nide separation and purification processes.[2,3] Additionally,
there has been interest stemming from use of phosphates
for the long term storage of actinides.[4–10] However, few
neptunium phosphates have been prepared as pure
phases.[11–16] More recently, actinide phosphonates have
been explored owing to their possible uses in these nuclear
processes.[17–22]
[a] Department of Civil Engineering and Geological Sciences and
Department of Chemistry and Biochemistry, University of
Notre Dame,
Results and Discussion
156 Fitzpatrick Hall, University of Notre Dame, Notre Dame,
Indiana 46556, USA
Fax: +1-574-631-9236
E-mail: talbrec1@nd.edu
Crystals of Cs[Np(H1.5PO4)(PO4)]2 obtained appeared
light green in color when illuminated by standard room
lighting, but under microscope lighting, the single plate-like
crystals were light pink. This type of dichroism is common
in NpIV compounds, and is termed the Alexandrite effect.
The resulting single phase product is shown in Figure 1,
and the crystallographic information is shown in Table 1.
[b] Institut für Geowissenschaften, Universität zu Kiel,
Ludevig-Meyn Str. 10, 24118 Kiel, Germany
[c] Forschungszentrum Jülich GmbH, Institute for Energy and
Climate Research (IEK-6),
52428 Jülich, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100464.
Eur. J. Inorg. Chem. 2011, 3749–3754
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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E. V. Alekseev, T. E. Albrecht-Schmitt et al.
FULL PAPER
All of the NpVI from the starting material was reduced by sharing phosphate, which contributes the last two bridging
P3+ to NpIV, which reacted with the oxidized phosphate to oxygen atoms. The average Np–O bond length from the cor-
form the product.
ner-sharing phosphates is 2.306(4) Å, whereas the average
Np–O bond length of the edge-sharing phosphates is con-
siderably longer at 2.504(4) Å (Table 2). The first coordina-
tion sphere of the NpIV atom is shown in Figure 2. Caesium
cations balance the charge in the interlayer space. See Sup-
porting Information for more information on the structure
and bond valence sum calculations.
Table 2. Selected bond lengths for Cs[Np(H1.5PO4)(PO4)]2.
Bond lengths (Å) for Cs[Np(H1.5PO4)(PO4)]2
Np(1)–O(7)
Np(1)–O(6)
Np(1)–O(4)
Np(1)–O(3)
Np(1)–O(1)
Np(1)–O(2)
Np(1)–O(2)Ј
Np(1)–O(3)
Cs(1)–O(5)
Cs(1)–O(5)Ј
Cs(1)–O(5)ЈЈ
2.216(4)
2.239(4)
2.315(4)
2.338(4)
2.362(4)
2.365(4)
2.471(4)
2.536(4)
3.032(4)
3.032(4)
3.203(5)
Cs(1)–O(8)ЈЈ
Cs(1)–O(8)ЈЈЈ 3.311(4)
3.311(4)
Cs(1)–O(4)
Cs(1)–O(4)Ј
Cs(1)–O(5)
Cs(1)–O(5)Ј
P(1)–O(6)
P(1)–O(7)
P(1)–O(3)
P(1)–O(2)
P(2)–O(1)
P(2)–O(4)
P(2)–O(5)
P(2)–O(8)
3.678(4)
3.678(4)
3.806(5)
3.806(5)
1.519(4)
1.520(4)
1.547(4)
1.551(4)
1.515(4)
1.521(5)
1.532(4)
1.588(5)
Figure 1. Cs[Np(H1.5PO4)(PO4)]2 viewed in the ac plane as a
double layer of neptunium(IV) phosphate with caesium cations in
the interlayers. Here the NpO8 units form edge-sharing chains.
These then form a double-layered sheet by way of the phosphate
units. The NpIV atoms are shown as green polyhedra, the phos-
phate anions are purple polyhedra, and the caesium atoms are
shown in light gray.
Cs(1)–O(5)ЈЈЈ 3.203(5)
Cs(1)–O(8)
Cs(1)–O(8)Ј
3.297(5)
3.297(5)
Table 1. Crystallographic data for Cs[Np(H1.5PO4)(PO4)]2 (A),
Np(HPO3)2(H2O)2 (B), U(HPO3)2(H2O)2 (C), and Th(HPO3)2-
(H2O)2 (D).
Compound
A
B
C
D
Mass
986.79
432.99
429.99
422.99
Color and habit
light pink pale green dark green colorless
plate
C2/c
column
Pbca
block
Pbca
block
Pbca
Space group
(No. 15)
(No. 61)
(No. 61)
(No. 61)
a /Å
b /Å
c /Å
29.449(4) 8.6672(8) 8.70230(10) 8.8482(2)
6.5800(8) 9.0152(5) 9.05920(10) 9.1711(2)
10.964(3) 18.267(2) 18.3558(3) 18.5259(5)
α /°
β /°
90
98.700(2) 90
90 90
90
90
90
90
90
90
90
γ /°
V /Å3
1323.4(3) 1427.3(2) 1447.10(3) 1503.33(6)
Z
4
8
8
8
T /K
100(2)
4.953
189.03
0.0239
100(2)
4.030
150.12
0.0154
103(2)
3.947
228.77
0.0170
100(2)
3.747
202.65
0.0424
ρcalcd. /gcm–3
μ(Mo-Kα) /cm–1
R(F) for
Figure 2. A thermal ellipsoid representation (90% probability) of
the neptunium(IV) center in Cs[Np(H1.5PO4)(PO4)]2 showing the
six corner-sharing and one edge-sharing phosphate anions. The
NpIV atom is shown in white, phosphorus atoms are in black, and
oxygen atoms are in gray.
Fo2 Ͼ 2σ(FBo )P[a]
Rw(FBo
CSD number
2
2 [b]
)
0.0472
423001
0.0296
423002
0.0441
423004
0.1257
423003
2
2 2
[a] R(F) = Σ||Fo| – |Fc||/Σ|Fo|. [b] Rw(Fo2) = {Σ[w(Fo – Fc ) ]/
4
1/2
ΣwFo
} .
Crystals of the first neptunium phosphite Np(HPO3)2-
This neptunium(IV) structure is based on double layers (H2O)2 were obtained in similar conditions as the neptuni-
formed by NpO8 and PO4 polyhedra (Figure 1). The NpO8 um(IV) phosphate, described above, but NpV was used as a
groups have approximate C2v symmetry (see Supporting In- starting material instead of NpVI. In this case, the neptu-
formation for values) with a bicapped trigonal prismatic nium is reduced by only one electron, leaving more of the
geometry determined using the algorithm developed by phosphite to react with the now reduced NpIV. As a result,
Raymond and coworkers.[32,33] The NpO8 units are linked a completely different product was obtained, but it was not
by their edges into a 1D chain, which then form double pure. The majority of the crystalline product was this new
layers through PO4 tetrahedral groups.
neptunium(IV) phosphite, and approximately 20% of the
In Cs[Np(H1.5PO4)(PO4)]2 there is only one crystallo- reaction mixture was found to be Cs[Np(H1.5PO4)(PO4)]2,
graphically unique position for neptunium. It is eight-coor- both by solid state UV/Vis/NIR spectroscopy and single-
dinate with six corner-sharing phosphates and one edge- crystal X-ray diffraction.
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Facile Routes to ThIV, UIV, and NpIV Phosphites and Phosphates
The pale green crystals of Np(HPO3)2(H2O)2 obtained Table 3. Selected bond lengths for An(HPO3)2(H2O)2.
were suitable for single-crystal X-ray diffraction, and a por-
Bond lengths (Å) for An(HPO3)2(H2O)2
An = Np4+
An = U4+
An = Th4+
tion of this structure is shown in Figure 3. The structure is
a dense 3D framework based on corner-sharing NpIV and
PIII polyhedra. The resulting NpO8 groups have approxi-
An(1)–O(8)
An(1)–O(3)
2.249(2)
2.260(2)
2.289(2)
2.315(2)
2.345(2)
2.350(2)
2.454(2)
2.491(3)
1.516(2)
1.516(2)
1.528(2)
1.517(2)
1.520(2)
1.528(2)
2.251(3)
2.262(3)
2.296(3)
2.323(3)
2.360(3)
2.380(3)
2.498(3)
2.528(3)
1.509(3)
1.522(3)
1.523(3)
1.513(3)
1.516(3)
1.527(3)
2.316(7)
2.332(7)
2.347(7)
2.378(7)
2.393(7)
2.410(7)
2.531(7)
2.574(7)
1.508(7)
1.519(8)
1.524(7)
1.511(8)
1.518(8)
1.538(7)
mate D2d symmetry with trigonal dodecahedral geome- An(1)–O(6)
try.[32,33] Six corner-sharing phosphite anions and two
An(1)–O(4)
An(1)–O(5)
bound water molecules surround each neptunium atom.
An(1)–O(7)
The local environment of the Np atoms in the structure of
An(1)–O(2)
Np(HPO3)2(H2O)2 is shown in Figure 4. The average bond
length for the bridging oxygen atoms is 2.301(2) Å, and the
average bond length for the bound water molecules is
2.473(3) Å (Table 3). Hydrogen atoms were located from the
difference maps for both the bound water molecules and
the phosphite centers.
An(1)–O(1)
P(1)–O(5)
P(1)–O(3)
P(1)–O(4)
P(2)–O(7)
P(2)–O(8)
P(2)–O(6)
The U(HPO3)2(H2O)2 and Th(HPO3)2(H2O)2 structures
are isotypic with Np(HPO3)2(H2O)2. Both of these phases
where obtained using similar conditions. The crystal struc-
tures of both show eight-coordinate UIV or ThIV centers.
The six corner-sharing phosphite anions and two bound
water molecules coordinate the actinide cations [as in
Np(HPO3)2(H2O)2 in Figure 4, see also Supporting Infor-
mation]. Unlike in the structure of NpIV phosphite, protons
could not be established on the bound water molecules for
the UIV/ThIV phosphite structures. The average U–OH2
bond length is 2.513(3) Å and 2.312(3) Å for the bridging
phosphite oxygens. Longer distances of 2.553(7) Å for Th–
OH2 and 2.363(7) Å for the bridging phosphites are found
in the Th structure. The UO8 and ThO8 groups within these
structures also have approximate D2d symmetry.[32,33]
As shown in Figure 5, transitions consistent with the
NpIV oxidation state are observed in the solid state UV/Vis/
NIR spectra of Cs[Np(H1.5PO4)(PO4)]2 and Np(HPO3)2-
(H2O)2; especially those at approximately 720 and
950 nm.[22,34,35] Interestingly, the peaks for the neptunium
phosphite are shifted to higher wavelengths than the neptu-
nium phosphate peaks. The reason for this shift could be
due to the different coordination environment at the two
NpIV centers. Although both are eight-coordinate, the
Figure 3. A depiction of the 3D network of An(HPO3)2(H2O)2 (An
= Th, U, Np) in the bc plane. The NpIV(HPO3)2(H2O)2 structure
is shown here but all three are isotypic. NpIV polyhedra are green,
the phosphite polyhedra are purple, and the hydrogen atoms are
shown in white.
Figure 4. The neptunium center in Np(HPO3)2(H2O)2 is shown in a
thermal ellipsoid (90% probability) representation. The neptunium
center has two bound water molecules and six corner-sharing phos-
phite tetrahedra. This structure is the same for the other two actin-
ide phosphites, save for the protons on the bound waters which
were not found from the difference maps for UIV/ThIV phosphites.
The NpIV atom is shown in white, the phosphorus atoms are in
black, the oxygen atoms are in dark gray, and the hydrogen atoms
are in light gray.
Figure 5. Solid state UV/Vis/NIR spectra for Np(HPO3)2(H2O)2,
shown in gray, and Cs[Np(H1.5PO4)(PO4)]2, shown in black.
Eur. J. Inorg. Chem. 2011, 3749–3754
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E. V. Alekseev, T. E. Albrecht-Schmitt et al.
FULL PAPER
phosphite has two bound water molecules, whereas the in the absence of cations, phosphite can quite easily mimic
phosphate has only bridging oxygen atoms from phosphate phosphate in these densely packed structures.
anions.
Although the actinide phosphites and the thorium phos-
3–
All three of the actinide phosphite compounds described phate structures have different ligands, both PO4 and
above are isotypic. The thorium phosphite synthesis in- HPO3 are essentially tetrahedral and the phosphorus–
2–
volved no redox chemistry, whereas the uranium phosphite oxygen bonds in the phosphite groups are slightly shorter
required an excess of phosphite, and the neptunium phos- than those of phosphate. The hydrogen atom on the P3+
phite required moving from NpVI to NpV in order to obtain atom in phosphite relaxes the tetrahedral symmetry and al-
the desired product. Table 4 shows a comparison of the unit lows less than ideal bond angles compared to those of the
cells, volumes, and average bond lengths for the three phos- normal phosphate tetrahedron. Even though the structures
phites, with UIV phosphite compared to ThIV phosphite appear very similar, the ThIV phosphate centers are seven-
and NpIV phosphite compared to UIV phosphite. The ex- coordinate and actinide phosphite centers are eight-coordi-
pansion in bond lengths from neptunium to uranium to nate. Regardless of this, in this simple, dense structure the
thorium is consistent with actinide contraction.
two compounds are quite similar because of same type of
heavy element packing (Figure 6).
Table 4. Comparison of the unit cells and bond lengths for
An(HPO3)2(H2O)2 (An = Th, U, Np).
Actinide
Th
U
Np
Conclusions
a /Å
b /Å
8.848
9.171
18.526
1503.35
2.553
–0.146
–0.112
–0.170
–56.25
–0.040
–0.051
–0.035
–0.044
–0.089
–19.80
–0.039
–0.011
The hydrothermal reactions of NpV and NpVI with phos-
phorous acid demonstrate that the formation of crystalline
products relies strongly on the solubility of the products
formed. Both reactions should have yielded NpIV phos-
phites, but this is not observed. When the reduction of NpVI
to NpIV occurs only one equivalent of the ten equivalents
of phosphite added is oxidized from H3PIIIO3 to H3PVO4;
nevertheless, the only product obtained from this reaction
was Cs[Np(H1.5PO4)(PO4)]2. When the reaction is changed
to the reduction of NpV to NpIV only half an equivalent of
H3PO3 is allowed to oxidize. Here we see that the majority
(va. 80%) of the product is neptunium(IV) phosphite and
the remainder is neptunium(IV) phosphate. It seems clear
that the solubility of Cs[Np(H1.5PO4)(PO4)]2 is probably
much less than that of Np(HPO3)2(H2O)2.
c /Å
V /Å3
Average An-OH2
Average An-O
2.363
The phosphite phases described above are quite similar
to a thorium(IV) phosphate, Th(HPO4)2(H2O), synthesized
by Garcia et al.[36] The unit cells are very close to the di-
mensions of Th(HPO4)2(H2O) and they share the same
Pbca space group [a = 9.1987(3), b = 18.6418(6), c =
8.7890(3) Å]. Looking at the overall structure (Figure 6)
one can see how similar they are. Here it can be seen how
This hypothesis is bolstered by the synthesis of U(HPO3)2-
(H2O)2. Here much of the uranium was still in the mother
liquor, and even when allowed to slowly evaporate, a vis-
cous liquid was all that was obtained. These results may be
greatly influenced by pH, which is most likely to be the
governing factor on the products formed. Here we have suc-
cessfully synthesized the first neptunium and thorium phos-
phites. We have also expanded the chemistry of uranium
phosphites. Additionally, we have shown that the source of
neptunium and the concentration of phosphite can greatly
influence the products formed. Thus far, it seems obvious
that solubility is the fundamental property that controls the
crystallization of these products and that the pH of the
starting solutions may greatly affect the products that form.
Experimental Section
Caution! 237Np (t1/2 = 2.14ϫ106 years) represents a serious health
risk owing to its α and γ emission, and especially because of its
decay to the short-lived isotope 233Pa (t1/2 = 27.0 d), which is a
potent β and γ emitter. All studies with neptunium were conducted
in a laboratory dedicated to studies on transuranium elements. This
laboratory is located in a nuclear science facility and is equipped
with HEPA filtered hoods and negative pressure gloveboxes that
are ported directly into the hoods. The laboratory is licensed by
Figure 6. A comparison of the structure of Th(HPO4)2(H2O) (top)
with that of Np(HPO3)2(H2O)2 (bottom). The two structures are
similar even though the bonding environments of the metal centers
are different, with eight-coordinate Np (shown in green) and seven-
coordinate Th (shown in aqua).
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Facile Routes to ThIV, UIV, and NpIV Phosphites and Phosphates
the Nuclear Regulatory Commission. All free-flowing solids are
manipulated in gloveboxes, and products are only examined when
coated with either water or Krytox oil and water. There are signifi-
cant limitations in accurately determining yield with neptunium be-
cause this requires drying, isolating, and weighing a solid, which
poses certain risks, as well as manipulation difficulties given the
small quantities employed in the reactions. Additionally, although
the UO2(NO3)2·6H2O used in this study contained depleted ura-
nium, standard precautions for handling radioactive materials,
such as uranyl nitrate and thorium nitrate, should be followed.
200 mmol), and H3PO3 (330.0 mg, 2.013 mol) into a 23 mL PTFE
autoclave liner with 2 mL of distilled water. This yields an approxi-
mate ratio of reactants of 2 Cs2CO3:UVI:20 H3PO3. The liner was
then sealed in a stainless steel autoclave and placed into a box
furnace. The reaction was then heated to 175 °C for 2 days and
then cooled at a rate of 7 °C per hour. The mother liquor from this
reaction was very dark green and a few very dark green crystals
were obtained. The block crystals were washed with water and the
mother liquor was saved.
Syntheses: UO2(NO3)2·6H2O (International Bio-analytical Indus-
tries, Inc.), Th(NO3)4·4H2O (Sigma–Aldrich), caesium carbonate
(Alfa-Aesar, 99.9%), and phosphorous acid (Alfa-Aesar, 97%)
were used as received. 237NpO2(s) (99.9%, Oak Ridge) was prepared
by the oxidation of triple electrorefined neptunium metal. A stock
solution of NpVI nitrate (0.372 m, 5 mg in 50 μL of water) was pre-
pared by first digesting NpO2(s) in 8 m HNO3 for 3 d at 200 °C (in
an autoclave). The resulting solution was reduced to a residue,
which oxidizes the neptunium to NpVI. This was then dissolved to
yield the desired concentration and then bubbled with ozone to
Th(HPO3)2(H2O)2: Th(HPO3)2(H2O)2 was synthesized by reacting
thorium nitrate (114.0 mg, 103 mmol), Cs2CO3 (130.0 mg,
199 mmol), and H3PO3 (328.2 mg, 2.002 mmol) in 2 mL of distilled
water. This gives a ratio of reactants of 2 Cs2CO3:ThIV:20 H3PO3.
The 23 mL PTFE liner was sealed in a stainless steel autoclave and
placed into a box furnace. The reaction was heated to 175 °C for 2
d and then cooled at a rate of 7 °C per hour. The product was
washed with water and most of the white product obtained was an
uncharacterized powder; however, a few colorless, block crystals
were found as well. These crystals were easily separated and were
suitable for single-crystal X-ray diffraction.
ensure that all of the neptunium was NpVI
.
Cs[Np(H1.5PO4)(PO4)]2: A reaction mixture of NpVI (50 μL,
175 mmol) from the stock solution, Cs2CO3 (11.2 mg, 344 mmol),
and H3PO3 (14.5 mg, 1.769 mol) was diluted to 0.1 mL with dis-
tilled water in a 10 mL PTFE autoclave liner. The reaction mixture
yields an approximate molar ratio of 2 Cs2CO3:NpVI:10 H3PO3.
The liner was placed in a stainless steel autoclave, which was sealed
and placed in a box furnace. This furnace was heated to 175 °C for
3 d and cooled at a rate of 5 °C per hour. Even when the time
of this reaction was shortened to just two hours the same pure
neptunium(IV) phosphate phase was obtained. The resulting crys-
tals exhibit the Alexandrite effect where they change color de-
pending on the lighting. In bulk under standard room lighting they
appear as light green plates, but under illumination with micro-
scope lighting they become light pink in color.
Crystallographic Studies: Crystals of all compounds were mounted
on CryoLoops with Krytox oil and optically aligned on a Bruker
APEXII Quazar X-ray diffractometer using a digital camera. Ini-
tial intensity measurements were performed using a IμS X-ray
source, a 30 W microfocused sealed tube (Mo-Kα, λ = 0.71073 Å)
with high-brilliance and high-performance focusing Quazar
multilayer optics. Standard APEXII software was used for determi-
nation of the unit cells and data collection control. The intensities
of reflections of a sphere were collected by a combination of four
sets of exposures (frames). Each set had a different φ angle for the
crystal and each exposure covered a range of 0.5° in ω. A total of
1464 frames with an exposure time of 10 seconds were used for
Cs[Np(H1.5PO4)(PO4)]2, 1464 frames with an exposure time of 30
seconds were used for Np(HPO3)2(H2O)2, 1076 frames with an ex-
posure time of 10 seconds were used for U(HPO3)2(H2O)2, and
1000 frames with an exposure time of 10 seconds were used for
Th(HPO3)2(H2O)2. SAINT software was used for data integration
including Lorentz and polarization corrections. Semiempirical ab-
sorption corrections were applied using the program SCALE (SA-
DABS).[37]
Np(HPO3)2(H2O)2: By changing the starting material from NpVI
nitrate to NpV hydroxide the final product can be drastically
changed. The NpVI stock solution described above was reduced to
NpV with excess NaNO2(s) and precipitated as the hydroxide by
adding excess ammonium hydroxide. The resulting NpVO2OH(s)
was washed repeatedly with water to remove all excess nitrate/ni-
trite. The reaction mixture to prepare Np(HPO3)2(H2O)2 consisted
of NpVO2OH(s) (4.9 mg, 171 mmol), Cs2CO3 (11.7 mg, 359 mmol),
and H3PO3 (14.9 mg, 1.817 mol). This was also diluted to 0.1 mL
with distilled water and placed in a 10 mL PTFE autoclave liner.
The molar ratio was the same as the reaction described above. The
stainless steel autoclave was sealed and placed into a box furnace,
which was headed to 175 °C for 3 d and cooled at a rate of 5 °C
per hour. The major product was Np(HPO3)2(H2O)2, which was
obtained as green, column-like crystals. About 20% of the reaction
mixture was light pink plates. This was found to be
Cs[Np(H1.5PO4)(PO4)]2 by single crystal X-ray diffraction and solid
state UV/Vis/NIR spectroscopy.
Further details on the crystal structure investigation may be ob-
tained from the Fachinformationszentrum Karlsruhe, 76344 Egg-
enstein-Leopoldshafen, Germany (fax: +49-7247-808-666; e-mail:
crysdata@fiz-karlsruhe.de), on quoting depository numbers CSD-
423001 to -423003. Selected bond lengths are given in Tables 2 and
3.
UV/Vis/NIR Spectroscopy: UV/Vis/NIR data were acquired from
single crystals of Cs[Np(H1.5PO4)(PO4)]2 and Np(HPO3)2(H2O)2
using a Craic Technologies microspectrophotometer. Crystals were
placed on quartz slides under Krytox oil, and the data were col-
lected from 400 to 1600 nm. The exposure time was auto optimized
by the Craic software.
Supporting Information (see footnote on the first page of this arti-
U(HPO3)2(H2O)2: U(HPO3)2(H2O)2 was synthesized by loading cle): Atomic coordinates and additional structural information
uranyl nitrate (101.5 mg, 101 mmol), Cs2CO3 (130.5 mg, (CIFs). Bond valence sum calculations, symmetry calculations, ad-
Eur. J. Inorg. Chem. 2011, 3749–3754
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3753

E. V. Alekseev, T. E. Albrecht-Schmitt et al.
FULL PAPER
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Received: May 2, 2011
Published Online: August 5, 2011
3754
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 3749–3754