A U(V) chalcogenide: Synthesis, structure, and characterization of K 2Cu3US5

Article abstract of DOI:10.1021/ic700774g

The compound K₂Cu₃US₅ was obtained by the reaction of K₂S, UCl₄, CuCl, and S at 973 K. K ₂Cu₃US₅ crystallizes in a new structure type in space group Cmcm of the orthorhombic system in a cell of dimensions a = 3.9374(6) A, b = 13.813(2) A, c = 17.500(3) A, and V = 951.8(2) A³ at 153 K. The structure comprises _∞²[UCu₃S₅^2-] slabs separated by K⁺ cations. The slabs are built from CuS₄ tetrahedra and US₆ octahedra. Their connectivity differs from other known octahedral/tetrahedral packing patterns. In the temperature range 130-300 K the compound exhibits Curie-Weiss magnetic behavior with μ_eff = 2.45(8) μ_B. This result together with both the bond distances and bond valence calculations and the absence of a Cu²⁺ ESR signal support the formulation of the above compound as K⁺ ₂Cu⁺₃U⁵⁺S^2-₅.

Full text of DOI:10.1021/ic700774g

Inorg. Chem. 2007, 46, 6992−6996
A U(V) Chalcogenide: Synthesis, Structure, and Characterization of
K2Cu3US5
Danielle L. Gray,† Lisa A. Backus,† Hans-Albrecht Krug von Nidda,‡ S. Skanthakumar,§ Alois Loidl,‡
L. Soderholm,§ and James A. Ibers*,†
Department of Chemistry, Northwestern UniVersity, EVanston, Illinois 60208, Institut fu¨r Physik,
UniVersita¨t Augsburg, Augsburg, Germany, and Chemistry DiVision, Argonne National
Laboratory, Argonne, Illinois 60439
Received April 23, 2007
The compound K2Cu3US5 was obtained by the reaction of K2S, UCl4, CuCl, and S at 973 K. K2Cu3US5 crystallizes
in a new structure type in space group Cmcm of the orthorhombic system in a cell of dimensions a
Å, b 13.813(2) Å, c 17.500(3) Å, and V
)
3.9374(6)
951.8(2) Å3 at 153 K. The structure comprises 2 [UCu3S5 -] slabs
2
)
)
)
∞
separated by K+ cations. The slabs are built from CuS4 tetrahedra and US6 octahedra. Their connectivity differs
from other known octahedral/tetrahedral packing patterns. In the temperature range 130 300 K the compound
B. This result together with both the bond distances
−
exhibits Curie−Weiss magnetic behavior with µeff ) 2.45(8) µ
and bond valence calculations and the absence of a Cu2+ ESR signal support the formulation of the above compound
-
as K+2Cu+3U5+S2
.
5
Introduction
sis5 of the magnetic measurements on ground single crystals
the compound was given a nonclassical formulation, namely
K+ Cu+ U5+2S2-13S- .
Although the chemistry of uranium is well documented,1
the literature on U5+ remains meager compared to that on
U3+, U4+, or U6+. This is not surprising because of the
tendency of U5+ in solution to disproportionate to U4+ and
6
12
2
4
In addition to K6Cu12U2S15 in the A/Cu/U/Q system (A
) alkali metal; Q ) S, Se, or Te) the compounds CsCuUTe3,6
8
KCuUSe3,7 and CsCuUSe3 are known. These three com-
U
6+ as well as the sensitivity of U5+ to oxidation. Compounds
pounds of U4+ adopt the robust KCuZrS3 structure type.9
We report here the synthesis, structure, and characterization
of the new A/Cu/U/Q compound K2Cu3US5. We present
evidence for a classical formulation of this compound as
of U5+ mainly comprise the halides, alkoxides, oxides, and
oxyhalides,2 but a few other types of compounds are also
known. A recent example3 of a U5+ compound is the silicate
K(UO)Si2O6, which contains a UO6 octahedron made up
from four equatorial silicate oxygen and two axial oxygen
atoms. Another recent compound is K6Cu12U2S15.4 There are
no S-S bonds in this compound so that charge balance could
have been achieved with Cu+, U6+, and S2-. However, from
conductivity measurements on pressed pellets and an analy-
K+ Cu+ U5+S2-
.
5
2
3
Experimental Section
Synthesis of K2Cu3US5. CCl4 was dried over KH and distilled.
The following reagents were used as obtained from the manufac-
turer: K (Cerac, 98%), S (Mallinckrodt, 99.6%), CuCl (Aldrich,
99+%), UO3 (Kerr-McGee Nuclear Corp.), and hexachloropropene
(Aldrich, 96%). K2S was prepared by the stoichiometric reaction
of the elements in liquid NH3. UCl4 was prepared by a modification
* To whom correspondence should be addressed. Phone: +1 847 491
5449. Fax: +1 847 491 2976. E-mail: ibers@chem.northwestern.edu.
† Northwestern University.
‡ Universita¨t Augsburg.
§ Argonne National Laboratory.
(1) Grenthe, I.; Drozdzynski, J.; Fujino, T.; Buck, E. C.; Albrecht-Schmitt,
T. E.; Wolf, S. F. In The Chemistry of the Actinide and Transactinide
Elements, Third ed.; Morss, L. R., Edelstein, N. M., Fuger, J., Eds.;
Springer: Dordrecht, 2006; Vol. 1, pp 253-698.
(5) Schilder, H.; Speldrich, M.; Lueken, H.; Sutorik, A. C.; Kanatzidis,
M. G. J. Alloys Compd. 2004, 374, 249-252.
(6) Cody, J. A.; Ibers, J. A. Inorg. Chem. 1995, 34, 3165-3172.
(7) Sutorik, A. C.; Albritton-Thomas, J.; Hogan, T.; Kannewurf, C. R.;
Kanatzidis, M. G. Chem. Mater. 1996, 8, 751-761.
(8) Huang, F. Q.; Mitchell, K.; Ibers, J. A. Inorg. Chem. 2001, 40, 5123-
5126.
(2) Selbin, J.; Ortego, J. D. Chem. ReV. 1969, 69, 657-671.
(3) Chen, C.-S.; Lee, S.-F.; Lii, K.-H. J. Am. Chem. Soc. 2005, 127,
12208-12209.
(4) Sutorik, A. C.; Patschke, R.; Schindler, J.; Kannewurf, C. R.;
Kanatzidis, M. G. Chem.sEur. J. 2000, 6, 1601-1607.
(9) Mansuetto, M. F.; Keane, P. M.; Ibers, J. A. J. Solid State Chem.
1992, 101, 257-264.
6992 Inorganic Chemistry, Vol. 46, No. 17, 2007
10.1021/ic700774g CCC: $37.00
© 2007 American Chemical Society
Published on Web 07/26/2007

A U(V) Chalcogenide
of the literature procedure.10 A 3.00 g (10.5 mmol) portion of UO3
was combined with 7.5 mL (53.2 mmol) of hexachloropropene in
a 150 mL round-bottom flask. The flask was fit with a condenser
and placed under an N2 atmosphere that was vented through a KOH
bubbler. The N2 had been passed over BASF catalyst at 80 °C and
then over Drierite to remove H2O and O2. The flask was gradually
heated to 130 °C. This initiated an exothermic reaction that turned
the solution into a deep-red color and released Cl2 gas. Once the
exothermic reaction was complete, the reaction mixture was allowed
to reflux at 158 °C for 3.5 h. The resulting green UCl4 was separated
from the solution by filtration through a cannula. Three successive
washes of the product with 10 mL portions of CCl4 were carried
out. Residual CCl4 was removed under vacuum.
The initial reaction mixture consisted of 14.3 mg of CuCl (0.14
mmol), 25.1 mg of UCl4 (0.066 mmol), and 21.5 mg of K2S (0.19
mmol). Under an Ar atmosphere in a glovebox, the reaction mixture
was loaded into a fused-silica tube that was evacuated to ∼104 Torr
and flame sealed. The tube was placed in a computer-controlled
furnace where it was heated to 623 K in 48 h, kept at 623 K for 48
h, heated again to 973 K in 72 h, and cooled at 14 K/h to 373 K,
when it was removed from the furnace. The product was washed
with deionized water to remove salt byproducts and was dried with
acetone. The compound characterized as K2Cu3US5 crystallizes as
black needles and plates. Once the composition was established, a
more rational synthesis was found. This proceeded from the reaction
mixture of CuCl (0.42 mmol), UCl4 (0.14 mmol), K2S (0.60 mmol),
and S (0.5 mmol). This mixture was subjected to the same heating
cycle as that of the initial reaction mixture. K2Cu3US5 was obtained
in 24 wt % yield relative to U. It is air and moisture stable for
several weeks. Semi-qualitative EDX analysis of selected crystals
with a Hitachi S 3500 SEM showed an average ratio of K:Cu:U:S
of 2:3:1:5. No Cl was detected.
Structure Determination. Single-crystal X-ray diffraction data
were collected with the use of graphite-monochromatized Mo KR
radiation (λ ) 0.71073 Å) at 153 K on a Bruker Smart 1000 CCD
diffractometer.11 The crystal-to-detector distance was 5.023 cm.
Crystal decay was monitored by re-collecting 50 initial frames at
the end of data collection. Data were collected by scan of 0.3° in
ω in groups of 606, 606, 606, and 606 frames at æ settings of 0°,
90°, 180°, and 270°. The exposure time was 15 s/frame. The
collection of intensity data was carried out with the program
SMART.11 Cell refinement and data reduction were carried out with
the use of the program SAINT,11 and face-indexed absorption
corrections were performed numerically with the use of the program
XPREP.12 Then the program SADABS11 was employed to make
incident beam and decay corrections.
The structure was solved with the direct methods program
SHELXS and refined with the full-matrix least-squares program
SHELXL of the SHELXTL suite of programs.12 The program
STRUCTURE TIDY13 was used to standardize the positional
parameters. Additional experimental details are shown in Table 1
and in Supporting Information. Selected metrical data are presented
in Table 2.
Table 1. Crystal Data and Structure Refinement for K2Cu3US5
formula mass (amu)
space group
Z
a (Å)
b (Å)
667.15
Cmcm
4
3.9374(6)
13.813(2)
17.500(3)
951.8(2)
T (K)
153(2)
0.71073
4.656
254.68
0.0229
0.0554
λ (Å)
Fc (g cm-3
)
µ (cm-1
R(F)a
)
c (Å)
Rw(F2)b
V (Å3)
a R(F) ) Σ||Fo| - |Fc||/Σ|Fo| for Fo > 2σ(Fo ). b Rw(Fo ) ) [Σ w(Fo
2
2
2
2
2
4
2
2
2
2
- Fc )2/ΣwFo ], w-1 ) σ2(Fo ) + (0.02 Fo )2 for Fo g 0; w-1 ) σ2(Fo )
2
for Fo < 0.
Table 2. Selected Distances (Å) and Angles (deg) for K2Cu3US5
Cu(1)-S(1)
2.356(1)
2.317(2)
2.3904(9)
2.356(1)
2.429(2)
2.6827(9)
2.587(1)
K(1)-S(1) × 2
K(1)-S(2)
K(1)-S(2) × 2
K(1)-S(3) × 3
Cu(1)-Cu(2)
Cu(1)-U(1)
3.236(1)
3.240(2)
3.295(2)
3.195(2)
2.7093(5)
3.2543(6)
Cu(1)-S(2)
Cu(1)-S(3) × 2
Cu(2)-S(3) × 2
Cu(2)-S(2) × 2
U(1)-S(2) × 4
U(1)-S(3) × 2
S(3)-U(1)-S(3)
S(2)-U(1)-S(2)
S(2)-U(1)-S(2)
S(2)-U(1)-S(3)
S(3)-Cu(1)-S(3)
S(3)-Cu(1)-S(1)
180
S(3)-Cu(1)-S(2)
S(2)-Cu(1)-S(1)
S(1)-Cu(2)-S(1)
S(1)-Cu(2)-S(3)
S(3)-Cu(2)-S(3)
105.34(4)
112.22(6)
113.34(9)
110.02(3)
102.94(8)
94.42(4)
85.58(4)
89.49(4)
110.89(6)
111.38(4)
were performed on two single crystals of K2Cu3US5 with the use
of a Bruker ELEXSYS E500 CW spectrometer equipped with a
continuous He-gas-flow cryostat (Oxford Instruments). Measure-
ments were made at both X-band (9.47 GHz) and Q-band (34 GHz)
frequencies. The ESR measurement detects the power P absorbed
by the sample from the transverse magnetic microwave field as a
function of the static magnetic field H. Fields up to 18 kOe were
used. The signal-to-noise ratio of the spectra was improved by
recording the derivative dP/dH with the use of a lock-in technique
with field modulation. The sensitivity of the spectrometer is about
1011-1013 spins/Oe line width.
Magnetic Susceptibility Measurements. The magnetic suscep-
tibility data were collected on a Quantum Design MPMS XL7
SQUID magnetometer from a 5 mg sample of ground single crystals
of K2Cu3US5 that had been loaded into a gelatin capsule. Variable-
temperature experiments were carried out between 5 and 320 K
with applied fields of 0.1, 1, 2, 5, and 10 kOe. Field measurements,
to a maximum of 30 kOe, were carried out at several temperatures.
Results
Synthesis. The synthesis of K2Cu3US5 proceeded from a
partial metathesis reaction of K2S, CuCl, UCl4, and S at a
reaction temperature of 973 K. Small black crystals of high
quality were obtained in approximately 24 wt % yield.
K2Cu3US5 is moderately stable in air.
Structure. K2Cu3US5 crystallizes in a new structure type
2
(Figure 1). The structure consists of [UCu3S52-] slabs
∞
separated by K+ centers. Each U atom, which is located at
a site of symmetry 2/m.., is octahedrally coordinated by six
S atoms. There are two crystallographically independent Cu
atoms in the asymmetric unit. The Cu(1) atom has site
symmetry m.. whereas the Cu(2) atom has site symmetry
Electron Spin Resonance Measurements. Electron spin reso-
nance (ESR) measurements in the temperature range 4.2-300 K
(10) Hermann, J. A.; Suttle, J. F. In Inorganic Synthesis; Moeller, T., Ed.;
McGraw-Hill Book Company: New York, 1957; Vol. 5, pp 143-
145.
(11) SMART Version 5.054 Data Collection and SAINT-Plus Version 6.45A
Data Processing Software for the SMART System; Bruker Analytical
X-Ray Instruments, Inc.: Madison, WI, U.S.A., 2003.
(12) Sheldrick, G. M. SHELXTL Version 6.14; Bruker Analytical X-Ray
Instruments, Inc.: Madison, WI, U.S.A., 2003.
mm... In the structure each is tetrahedrally coordinated by
2
four S atoms. Figure 2 shows a [UCu3S52-] layer. Within
∞
each layer, US6 octahedra edge share and CuS4 tetrahedra
corner share with like polyhedra along the [100] direction
to form chains. The US6 octahedra edge share with four Cu-
(13) Gelato, L. M.; Parthe´, E. J. Appl. Crystallogr. 1987, 20, 139-143.
Inorganic Chemistry, Vol. 46, No. 17, 2007 6993

Gray et al.
Figure 3. 2 [K2S58-] layer as viewed down [010].
∞
Electron Spin Resonance. Two single crystals of K2Cu3US5
(with an estimated spin concentration of about 1015 Cu spins,
if Cu2+ were present in the compound) have been measured
between 4.2 and 300 K at 9.47 and 34 GHz. No signal was
detectable, and there was no indication of even a slight
deviation from background. Neither a Cu2+ nor a U signal
was visible.
Figure 1. Structure of K2Cu3US5 as viewed down [100].
The absence of a U signal is not surprising. Uranium
signals can be too broad to detect because of strong spin-
orbit coupling and fast spin fluctuations. This phenomenon
is also seen in some Ce compounds such as CeNiSn.17
Because of strong relaxation, a Cu2+ signal can be too broad
to detect as is the case in the high-temperature supercon-
ducting cuprates.18 On the other hand, in one-dimensional
spin 1/2 systems with Cu2+ or V4+ the signal is often detected
and can be narrow as, for example, in CuGeO3.19 In principle,
if the Cu2+:Cu+ ratio in K2Cu3US5 were 1:2, the situation
Figure 2. 2 [UCu3S52-] layer as viewed down [010].
20
would be similar to that in Na1/3V2O5 where the V4+:V5+
∞
ratio is 1:5. In Na1/3V2O5 the electrons are localized at low
temperatures and a narrow ESR signal was detected. The
signal broadened with increasing temperature.
(1)S4 tetrahedra, thereby connecting the U chains to Cu(1)
chains on both sides in the [001] direction. Each Cu(1)S4
tetrahedron edge shares with two US6 octahedra on one side
and two Cu(2)S4 tetrahedra on the other. The chains pack
Magnetic Susceptibility Measurements. The magnetic
susceptibility of K2Cu3US5 obtained as a function of tem-
perature under a small applied field is shown in Figure 4.
For the purpose of interpretation, the data are considered
within two different temperature regimes: above 130 K
where the behavior can be described in terms of noninter-
acting spins, and below 108 K where there is evidence of
magnetic correlations. Considering first the higher-temper-
ature regime, we depict in Figure 5 the field dependence of
the magnetic response obtained at 300 K. When one is
interpreting susceptibility data, the magnetic response is
normally assumed to be linear over the field range used to
determine the magnetization; it is the slope of the M versus
H curve that is the magnetic susceptibility at the temperature
along [001] in a U(1)oct, Cu(1)tet, Cu(2)tet, Cu(1)tet, U(1)-
2
oct pattern to form the [UCu3S52-] layer. This connectiv-
∞
2
∞
ity within the [UCu3S52-] layer is different from other
known octahedral/tetrahedral packing patterns. In NaCuTiS314
the connectivity within the layer is oct oct tet tet oct oct, in
NaCuZrS314 it is oct tet oct tet oct tet, in Na2Cu2ZrS415 it is
16
oct tet tet oct tet tet, and in K3Cu3Th2S7 the connectivity
within the layer is oct tet oct tet tet.
Each K center, located at a site with symmetry m.., is
coordinated by a capped trigonal prism of seven S atoms.
Each capped trigonal prism has two face-sharing neighbors
along [100] and three edge-sharing ones along [001] to form
a
2∞[K2S58-] layer, as shown in Figure 3.
(17) Mair, S.; Krug von Nidda, H.-A.; Lohmann, M.; Loidl, A. Phys. ReV.
B 1999, 60, 16409-16414.
(18) Elschner, B.; Loidl, A. In Handbook on the Physics and Chemistry of
the Rare Earths; Gschneidner, K. A., Jr., Eyring, L., Maple, M. B.,
Eds.; Elsevier: Amsterdam, 2000; Vol. 30, pp 375-415.
(19) Eremina, R. M.; Eremin, M. V.; Glazkov, V. N.; Krug Von Nidda,
H.-A.; Loidl, A. Phys. ReV. B 2003, 68, 014417-1-014417-10.
(20) Riedel, E.; Karl, R.; Rackwitz, R. Mater. Res. Bull. 1977, 12, 599-
603.
(14) Mansuetto, M. F.; Keane, P. M.; Ibers, J. A. J. Solid State Chem.
1993, 105, 580-587.
(15) Mansuetto, M. F.; Ibers, J. A. J. Solid State Chem. 1995, 117, 30-
33.
(16) Llanos, J.; Corte´s, R.; Guizouarn, T.; Pen˜a, O. Mater. Res. Bull. 2006,
41, 1266-1271.
6994 Inorganic Chemistry, Vol. 46, No. 17, 2007

A U(V) Chalcogenide
Figure 4. Magnetic susceptibility of K2Cu3US5 obtained as a function of
temperature under an applied field of 100 Oe.
Figure 6. Inverse susceptibility per formula unit of K2Cu3US5 plotted as
a function of temperature. This plot was obtained by subtracting from each
magnetization point obtained under an applied field of 5000 Oe the
corresponding point obtained under an applied field of 2000 Oe. The fit to
the Curie-Weiss equation is shown as a solid line.
higher than the temperature range of the experiment. A
possible source of such a ferromagnetic contribution is
metallic Fe. A total of about 0.005 wt %, that is 0.25 µg of
Fe in the 5 mg sample, would account for the observation.
That amount would go undetected analytically.
A representative plot of inverse magnetic susceptibility
versus temperature obtained in this manner is shown in
Figure 6. The data are linear over the temperature range of
130-300 K, indicating classical Curie-Weiss behavior, ø
) C/(T - Θ), in which C is the Curie constant, related to
the effective moment by µeff ) (8C)1/2, and Θ is the Weiss
constant, a term meant to account for moment correlations
or the influence of low-lying crystal-field states. From a least-
squares fit to these data we find an effective moment µeff of
2.45(8) µB and a Weiss constant of 4(1) K.
Figure 5. Magnetization per formula unit of K2Cu3US5 plotted as a
function of field measured at 300 K.
The magnetic response shows deviations from the behavior
expected for a classic paramagnet at temperatures below 108
K. A sharp increase in the susceptibility is observed over
the temperature range 94-105 K with a minimum in the
first derivative at 104(2) K. There is a sudden change of
slope at 94(2) K with a decreasing susceptibility observed
between about 94 and 20 K. At even lower temperatures,
there is an upturn in the measured signal with decreasing
temperature. Despite the general cusp in the susceptibility
over the temperature range of about 50-104 K, the overall
complex response is not indicative of a simple antiferro-
magnetic ordering. Instead, the low-temperature response
appears to have a complex origin, which could involve a
magnetic or a structural phase change, the latter of which
could be coupled with Cu-U charge transfer.
of the measurement. It can be seen from Figure 5 that the
response is nonlinear at fields lower than 1000 G. Above
this applied field, this contribution to the measured magne-
tization becomes field independent and an additive constant
to the total magnetization. This field-independent term, 5.38
× 10-5 emu at 300 K, represents about 10% of the measured
response from our 5 mg sample at a field of 30 kOe.
The field-independent term may be removed from the
measurements by obtaining M versus T data under several
different applied fields (1, 2, 5, and 10 kOe) and subtracting
data from two different fields. Comparing difference data
from the combination of different applied fields revealed that
this procedure produced susceptibility versus temperature
data that agreed within 2% accuracy for applied fields >2
kOe. The origin of the field-independent magnetization is
unknown, but such behavior is often interpreted in terms of
a saturated ferromagnetic component. In the present instance,
the field-independent magnetization is consistent with a
ferromagnetic contribution with ordering temperature much
Discussion
There are no S-S bonds in the structure of K2Cu3US5,
the shortest S‚‚‚S interaction being 3.645 Å. Therefore, the
Inorganic Chemistry, Vol. 46, No. 17, 2007 6995

Gray et al.
3
formal oxidation state of S in K2Cu3US5 may be assigned
as -2. Thus, the combined formal oxidation states of three
Cu atoms and one U atom must be +8 to achieve charge
balance. This can be accomplished with three Cu+ and one
unpaired f spins and a H4 ground term has a free-ion
effective moment of 3.58 µB.27 Assuming these values, we
find that the formal oxidation-state model (i), involving U5+,
has a free-ion calculated moment of 2.54 µB whereas the
model (ii), which includes U4+ and Cu2+, has a calculated
moment of 3.98 µB. The close correspondence of the
measured moment of 2.45(8) µB to that of 2.54 µB for model
(i) is corroborative evidence for the presence of U5+ in the
sample.
U
5+ or two Cu+, one Cu2+, and one U4+. The Cu2+ oxidation
state is rarely, if ever, found in sulfides, which makes it likely
that K2Cu3US5 is a compound of U5+. The absence of a Cu2+
ESR signal also suggests U5+. Further, indirect evidence for
this comes from the bond distances. Although the Cu-S
distances, ranging from 2.317(2) to 2.429(2) Å, are normal
(e.g., 2.319(1)-2.540(2) Å in RbEr2Cu3S521 and 2.305(1)-
2.381(1) Å in Ba2Cu2US522), the U-S distances of 2.587(1)
and 2.6827(9) Å are shorter than those in most US6 octahedra
In summary, the structural evidence, the valence bond
calculation, the absence of a Cu2+ ESR signal, and the µeff
value are all consistent with K2Cu3US5 being a classical
compound containing the rare oxidation state U5+.
that involve U4+, for example, 2.680(5)-2.709(5) Å in
23,24
BaUS3
and 2.673(2)-2.770(1) Å in Ba2Cu2US5.22
Acknowledgment. Funding for this work was kindly
provided: to Northwestern University by U.S. Department
of Energy Grant BES ER-15522, to Universita¨t Augsburg
by the German Bundesministerium fu¨r Bildung and Fors-
chung (BMBF) under contract number VDI/EKM 13N6917
and by Deutsche Forschungsgemeinschaft within Sonder-
forschungsbereich SFB 484, and to Argonne National
Laboratory by the U.S. DOE-OBES-Chemical Sciences
under Contract DE-AC02-06CH11357.
Bond valence sums25 of U ) 4.732, Cu(1) ) 1.029, and
Cu(2) ) 0.952 also suggest the presence of U5+.
Finally, the value of µeff of 2.45(8) µB may be compared
to the corresponding values of the two proposed models for
formal oxidation states within the compound K2Cu3US5: (i)
three Cu+ and one U5+, or (ii) one Cu2+, two Cu+, and one
U4+. Cu+ has no temperature dependence to its susceptibility
whereas Cu2+ has one unpaired d spin and a spin-only
effective moment of 1.73 µB. U5+, an 1f spin system modeled
within the Russell-Saunders coupling formalism,26 has a
free-ion effective moment of 2.54 µB whereas U4+ with two
Supporting Information Available: The crystallographic file
in CIF format for K2Cu3US5. This information is available free of
charge via the Internet at http://pubs.acs.org.
(21) Huang, F. Q.; Ibers, J. A. J. Solid State Chem. 2001, 158, 299-306.
(22) Zeng, H.-Y.; Yao, J.; Ibers, J. A. Unpublished work.
(23) Lelieveld, R.; IJdo, D. J. W. Acta Crystallogr., Sect. B: Struct.
Crystallogr. Cryst. Chem. 1980, 36, 2223-2226.
IC700774G
(26) Staub, U.; Soderholm, L. In Handbook on the Physics and Chemistry
of Rare Earths; Gschneidner, K. A., Jr., Eyring, L., Maple, M. B.,
Eds.; Elsevier: Amsterdam, 2000; Vol. 30, pp 491-545.
(27) Pitzer, K. S. Quantum Chemistry; Prentice Hall: New York, 1953; p
529.
(24) Brochu, R.; Padiou, J.; Grandjean, D. C. R. Seances Acad. Sci., Ser.
C 1970, 271, 642-643.
(25) O’Keeffe, M. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor.
Gen. Crystallogr. 1990, 46, 138-142.
6996 Inorganic Chemistry, Vol. 46, No. 17, 2007