Syntheses, structures, and magnetic and optical properties of the compounds [Hg3Te2][UCl6] and [Hg4As2][UCl6]

Article abstract of DOI:10.1016/j.jssc.2008.08.019

Two new quaternary salts, [Hg₃Te₂][UCl₆] and [Hg₄As₂][UCl₆], have been synthesized and their structures determined by single-crystal X-ray diffraction analysis. [Hg₃Te₂][UCl₆] is the product of a reaction involving UCl₄, HgCl₂, and HgTe at 873 K. The compound crystallizes in space group P2₁/c of the monoclinic system. [Hg₄As₂][UCl₆] results from the reaction of U, Hg₂Cl₂, and As at 788 K. It crystallizes in space group Pbca of the orthorhombic system. [Hg₃Te₂][UCl₆] has a two-dimensional framework of _∞² [Hg₃ Te₂^{2 +}] layers, whereas [Hg₄As₂][UCl₆] has a three-dimensional framework of _∞² [Hg₃ As₂] layers interconnected by Hg atoms linearly bonded to As atoms. Both framework structures contain discrete [UCl₆]^2- anions between the layers. [Hg₃Te₂][UCl₆] exhibits temperature-independent paramagnetism. The optical absorption spectra of these compounds display f-f transitions.

Full text of DOI:10.1016/j.jssc.2008.08.019

ARTICLE IN PRESS
Journal of Solid State Chemistry 181 (2008) 3189–3193
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
Syntheses, structures, and magnetic and optical properties of the compounds
[
Hg Te ][UCl ] and [Hg As ][UCl ]
3 2 6 4 2 6
Ã
Daniel E. Bugaris, James A. Ibers
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Two new quaternary salts, [Hg Te ][UCl ] and [Hg As ][UCl ], have been synthesized and their
3
2
6
4
2
6
Received 1 May 2008
Received in revised form
3 2 6
structures determined by single-crystal X-ray diffraction analysis. [Hg Te ][UCl ] is the product of a
reaction involving UCl
4
, HgCl
2
, and HgTe at 873 K. The compound crystallizes in space group P2
] results from the reaction of U, Hg Cl , and As at 788 K. It crystallizes
Te ][UCl ] has a two-dimensional framework of
1
/c of the
7
August 2008
monoclinic system. [Hg
4
As ][UCl
2
6
2
2
Accepted 11 August 2008
Available online 22 August 2008
in space group Pbca of the orthorhombic system. [Hg
3
2
6
2
2þ
] has a three-dimensional framework of 2 ½Hg As
ꢁ layers
½
Hg Te2 ꢁ layers, whereas [Hg
4
As
2
][UCl
6
2
1
3
1
3
Keywords:
interconnected by Hg atoms linearly bonded to As atoms. Both framework structures contain discrete
Uranium mercury chalcogenide
Uranium mercury pnictide
2ꢀ
[
UCl
6
]
anions between the layers. [Hg Te ][UCl ] exhibits temperature-independent paramagnetism.
3 2 6
The optical absorption spectra of these compounds display f–f transitions.
2008 Elsevier Inc. All rights reserved.
2
ꢀ
[
UCl ]
6
&
Crystal structures
Syntheses
1.
Introduction
2. Experimental
The vast majority of uranium transition-metal chalcogenides
2.1. Syntheses
(S, Se, or Te) or pnictides (P, As, Sb, or Bi) whose structures are
known incorporate 3d or 4d transition metals. The few with 5d
transition metals that have been studied by single-crystal X-ray
CCl4 was dried over KH and distilled. UCl4 was prepared by a
modification of the literature procedure [16]. A 6.02 g (21.0 mmol)
portion of UO3 (Kerr-McGee Nuclear Corp.) was combined
with 14.85 mL (105.3 mmol) of hexachloropropene (Aldrich, 96%)
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
diffraction methods include Cs
HfU Sb [3], and AuUSb [4]. To probe 5d/5f systems, we have
chosen the Hg/U system for which the binary phase diagram [5]
reveals only the phases Hg45 11, Hg U, Hg U, and HgU. We have
8 5 2 6
Hf UTe30.6 [1], Ir U Se15.5 [2],
3
5
2
U
3
2
probed this system with the use of mercury halides as reagents.
These reagents have been shown to react with metals and
chalcogens or pnictogens to produce quaternary compounds,
most of which are nothing more than salts but most of which have
been described as ‘‘supramolecular compounds’’. The chemistry of
353 K and then over Drierite to remove O2 and H O. The flask
2
was gradually heated to 403 K. This initiated an exothermic
reaction that turned the solution into a deep-red color and
released Cl2 gas. Once the reaction was complete, the reaction
mixture was allowed to reflux at 431 K for 3.5 h. The resulting
such compounds is rich and includes [Hg
3
Q
2
][SiF
] (Q ¼ S, Se; M ¼ Zr, Hf; X ¼ Cl, Br) [7], [Hg
][MX
]X (T ¼ P, As; M ¼ Mo, Ti; X ¼ Cl, Br)
[11], [Hg ][TlX
] (T ¼ As, Sb; X ¼ Cl, Br)
]Br [13], [Hg11As ][GaBr [14], and
[15]. Here we report the syntheses, crystal
6
] (Q ¼ S, Se, Te)
[
[
[
[
[
6], [Hg
Se ] [8], [Hg
9,10], [Hg As ][AgI
12], [Hg As ][YbBr
Hg As] [CdI
3
Q
2
][MX
6
3
Se
2
]
green UCl was separated from the solution by filtration through a
4
2
O
5
6
T
4
6
cannula. Three successive washes of the product with 10 mL
portions of CCl4 were carried out. Residual CCl4 was removed
under vacuum.
Finely divided uranium powder was prepared by a modifica-
tion of the literature procedure [17]. Uranium metal turnings
(depleted, Oak Ridge National Laboratory) were washed with
concentrated HNO3 to remove any uranium oxide coating. The
turnings were then rinsed with de-ionized water and dried with
acetone. The uranium metal turnings were placed in a Schlenk
7
4
3
]
2
3
T
2
3
6
4
6
4
4 4
]
2
2
4
]
structures, optical properties, and magnetic properties of the first
Hg/U chalcogenides or pnictides, namely [Hg Te ][UCl ] and
3
2
6
[
4 2 6
Hg As ][UCl ].
vessel and reacted with an atmosphere of H
UH . UH was converted to finely divided U powder under vacuum
at 773 K.
2
at 723 K to produce
Ã
Corresponding author.
3
3
E-mail address: ibers@chem.northwestern.edu (J.A. Ibers).
0
022-4596/$ - see front matter & 2008 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2008.08.019

ARTICLE IN PRESS
3190
D.E. Bugaris, J.A. Ibers / Journal of Solid State Chemistry 181 (2008) 3189–3193
The remaining reactants were used as obtained. Reactions
Table 1
a
Crystal data and structure refinements for [Hg
3
Te
2
][UCl
6
] and [Hg
4
As
2
][UCl
6
]
were carried out in fused-silica tubes. The tubes were charged
with reaction mixtures under an Ar atmosphere in a glove box
and then they were evacuated to ꢂ10ꢀ Torr and flame sealed.
Selected single crystals from each reaction were examined with an
EDX-equipped Hitachi S-3400 SEM. The compounds are both
moderately stable in air.
[
Hg
3
Te
2
][UCl
6
]
[Hg
4
As ][UCl ]
2
6
4
Fw
1307.70
P2 /c
1402.93
Pbca
8
Space group
1
Z
2
a ( A˚ )
b ( A˚ )
c ( A˚ )
6.835(1)
7.864(1)
13.632(2)
91.530(2)
732.4(2)
5.929
13.316(1)
13.636(1)
16.853(2)
90
2
3 2 6
.2. Synthesis of [Hg Te ][UCl ]
b
(1)
V (A˚
3
)
3060.0(5)
6.090
The reaction mixture consisted of UCl
0.22 mmol; Aldrich Chemical Co.), and HgCl
Mallinckrodt, Inc.). The reaction mixture was heated to 1123 K in
4 h, kept at 1123 K for 96 h, cooled at 6.8 K/h to 473 K, and then
cooled rapidly to 293 K. Green plates of [Hg Te ][UCl ] in about
0% yield were the major product, and green needles of UCl were
4
(0.11 mmol), HgTe
3
r
m
c
(g/cm )
(
2
(0.11 mmol;
ꢀ1
(cm
b
)
473.2
558.5
R(F)
0.038
0.033
2
c
R
w
(F )
0.109
0.083
2
3
2
6
a
˚
For both structures, T ¼ 153(2) K and
l
¼ 0.71073 A.
7
4
b
c
2
o
2
o
R(F) ¼
S
o0,
JF
o
jꢀjF
c
ꢀ1
J/
S
jF
o
j for F
42
s
(F
).
the minor product. In an alternative heating procedure, the
reaction mixture was heated to 873 K in 15 h, kept at 873 K for
20 h, and then the furnace was turned off. This synthesis
2
o
2
2
2
o
ꢀ1
2
2
o
2
For
F
w
¼
s
(F
o
); for
F
X0,
w
¼
s
(F
)+(0.0501 ꢃ P) +33.397 ꢃ
ꢀ
1
2
2
o
2
P ([Hg Te ][UCl ]); w
3
2
6
¼
s
(F )+(0.0197 ꢃ P) +133.94 ꢃ P ([Hg As ][UCl ]); P ¼
4
2
6
2
o
2
c
1
(F
+2 ꢃ F
)/3.
produced larger crystals of [Hg Te ][UCl ] suitable for further
3
2
6
measurements. EDX analysis of the green crystals showed the
presence of Hg, Te, U, and Cl.
Table 2
Selected interatomic distances (A) and angles (deg) for [Hg
˚
3 2 6
Te ][UCl ]
a
U–Cl(1) ꢃ 2
2.622(3)
2.623(3)
2.624(3)
2.664(1)
2.666(1)
2.672(1)
2
4 2 6
.3. Synthesis of [Hg As ][UCl ]
U–Cl(2) ꢃ 2
U–Cl(3) ꢃ 2
We have prepared single crystals of [Hg
reaction of U (0.13 mmol), Hg Cl (0.38 mmol; Alfa), and As
0.51 mmol; Strem Chemicals, Inc., 2N). The sample was heated
to 788 K in 12 h, kept at 788 K for 144 h, and then the furnace was
turned off. The product consisted of red blocks of [Hg As ][UCl
4
As
2
][UCl
6
] by the
Hg(1)–Te
Hg(1)–Te
2
2
Hg(2)–Te ꢃ 2
Cl–U–Cl
(
180
Cl(1)–U–Cl(2) ꢃ 2
Cl(1)–U–Cl(3) ꢃ 2
Cl(2)–U–Cl(3) ꢃ 2
Te–Hg(1)–Te
Te–Hg(2)–Te
Hg(1)–Te–Hg(1)
Hg(1)–Te–Hg(2)
Hg(1)–Te–Hg(2)
88.20(10)
88.35(10)
89.06(10)
172.82(2)
180
4
2
6
]
in about 80% yield. EDX analysis of the crystals showed the
presence of Hg, As, U, and Cl.
95.48(3)
94.64(3)
96.35(3)
2.4. Structure determinations
Single-crystal X-ray diffraction data were collected with the use
˚
a
U and Hg(2) have crystallographic site symmetry 1.
of graphite-monochromatized MoK
1
a radiation (l ¼ 0.71073A) at
53K on a Bruker Smart-1000 CCD diffractometer [18]. The crystal-
to-detector distance was 5.023 cm. Crystal decay was monitored by
recollecting 50 initial frames at the end of the data collection. Data
Table 3
Selected interatomic distances ( A˚ ) and angles (deg) for [Hg As ][UCl ]
4
2
6
were collected by a scan of 0.31 in
settings of 01, 901, 1801, and 2701. The exposure times for
Hg Te ][UCl ] and [Hg As ][UCl ] were 30 and 25 s/frame, respec-
tively. The collection of intensity data was carried out with the
program SMART [18]. Cell refinement and data reduction were
carried out with the use of the program APEX2 [19]. A Leitz
microscope equipped with a calibrated traveling micrometer eye-
piece was employed to measure accurately the crystal dimensions;
face-indexed absorption corrections were performed numerically
with the use of the program XPREP [20]. Then the program SADABS
o in groups of 606 frames at j
U–Cl(1)
2.605(3)
2.620(3)
2.624(3)
2.625(3)
2.629(3)
2.639(3)
2.480(1)
2.480(1)
2.467(1)
2.469(1)
2.462(1)
2.464(1)
2.485(1)
2.481(1)
Cl(2)–U–Cl(6)
Cl(3)–U–Cl(4)
Cl(3)–U–Cl(5)
Cl(3)–U–Cl(6)
Cl(4)–U–Cl(5)
Cl(4)–U–Cl(6)
Cl(5)–U–Cl(6)
86.4(1)
92.1(1)
U–Cl(2)
[
3
2
6
4
2
6
U–Cl(3)
93.1(1)
U–Cl(4)
90.1(1)
U–Cl(5)
90.5(1)
U–Cl(6)
177.8(1)
89.8(1)
Hg(1)–As(1)
Hg(1)–As(2)
Hg(2)–As(1)
Hg(2)–As(2)
Hg(3)–As(1)
Hg(3)–As(2)
Hg(4)–As(1)
Hg(4)–As(2)
As(1)–Hg(1)–As(2)
As(1)–Hg(2)–As(2)
As(1)–Hg(3)–As(2)
As(1)–Hg(4)–As(2)
Hg(1)–As(1)–Hg(2)
Hg(1)–As(1)–Hg(3)
Hg(1)–As(1)–Hg(4)
Hg(2)–As(1)–Hg(3)
Hg(2)–As(1)–Hg(4)
Hg(3)–As(1)–Hg(4)
Hg(1)–As(2)–Hg(2)
Hg(1)–As(2)–Hg(3)
Hg(1)–As(2)–Hg(4)
Hg(2)–As(2)–Hg(3)
Hg(2)–As(2)–Hg(4)
Hg(3)–As(2)–Hg(4)
161.51(4)
175.73(4)
175.67(4)
167.96(4)
118.98(5)
108.41(4)
103.59(4)
107.32(4)
111.66(5)
106.19(5)
117.86(5)
108.76(4)
106.91(4)
102.82(4)
106.57(4)
114.19(5)
[18] was employed to make incident beam and decay corrections.
The structures were solved with the direct methods program
SHELXS and refined with the full-matrix least-squares program
SHELXL [20]. Each final refinement included anisotropic displace-
ment parameters. The program STRUCTURE TIDY [21] was used to
standardize the positional parameters. Additional experimental
details are given in Table 1 and the Supporting material. Selected
metrical details are presented in Tables 2 and 3.
Cl(1)–U–Cl(2)
Cl(1)–U–Cl(3)
Cl(1)–U–Cl(4)
Cl(1)–U–Cl(5)
Cl(1)–U–Cl(6)
Cl(2)–U–Cl(3)
Cl(2)–U–Cl(4)
Cl(2)–U–Cl(5)
90.2(1)
179.3(1)
88.6(1)
86.6(1)
89.3(1)
90.0(1)
93.2(1)
175.1(1)
2.5. Magnetic susceptibility measurement
DC magnetic measurements of [Hg Te ][UCl ] were carried out
3
2 6
with the use of a Quantum Design MPMS5 SQUID magnetometer.
Twenty-seven milligrams of ground single crystals were loaded
into a gelatin capsule. Both zero-field cooled (ZFC) and field-
cooled (FC) measurements were made between 2 and 400 K with
a measuring field of 500 G. All data were corrected for electron
core diamagnetism [22].

ARTICLE IN PRESS
D.E. Bugaris, J.A. Ibers / Journal of Solid State Chemistry 181 (2008) 3189–3193
3191
2.6. Single-crystal optical measurements
Absorption measurements with polarized light were per-
formed over the range from 400 nm (3.10 eV) to 900 nm
1.38 eV) at 293 K on single crystals of [Hg Te ][UCl ] (green)
and [Hg As ][UCl ] (red) with the use of a Nikon TE300 inverted
(
3
2
6
4
2
6
microscope coupled by fiber optics to an Ocean Optics model
S2000 spectrometer. The procedure used has been described
previously [23].
3. Results and discussion
3.1. Syntheses
3 2 6
Fig. 1. The structure of [Hg Te ][UCl ] viewed down a*.
Green single crystals of [Hg
0 wt% yield by the stoichiometric reaction of UCl
3
Te
2
][UCl
6
] were obtained in
, HgCl , and
7
4
2
HgTe at 1123 K. Larger single crystals were obtained by lowering
the reaction temperature to 873 K, and increasing the reaction
time from 96 to 120 h. Red single crystals of [Hg
4
2 6
As ][UCl ] were
2 2
produced by the reaction of U, As, and Hg Cl at 788 K in 80 wt%
yield relative to U.
The compounds [Hg
in crystalline form from the stoichiometric reactions of UCl
HgCl
, and HgQ (Q ¼ S, Se) at 1123 K. Twinning and absorption
problems (owing to irregular crystal shapes) resulted in poor
structure determinations. The unit-cell constants—[Hg ][UCl ]:
3
Q
2
][UCl
6
] (Q ¼ S, Se) were also obtained
4
,
2
3
S
2
6
˚
˚
˚
a ¼ 6.865(5) A, b ¼ 7.368(5) A, c ¼ 13.143(8) A,
b
¼ 91.339(8)1;
˚
˚
˚
[
Hg
3
Se
2
][UCl
6
]: a ¼ 6.830(1) A, b ¼ 7.520(2) A, c ¼ 13.300(3) A,
Fig. 2. Chair conformation of the Hg
010].
6 6 3 2 6
Te rings in [Hg Te ][UCl ] viewed down
b
¼ 91.88(3)1—and the structure refinements, however, show
unequivocally that these compounds are isostructural with
Hg Te ][UCl ].
Attempts to synthesize analogues with different halides or
pnictides proved unsuccessful. The reaction of UBr , Hg Br , and
HgTe to produce [Hg Te ][UBr ] resulted only in the recrystalliza-
tion of UBr . The stoichiometric reaction of UI , HgI , and HgTe to
produce [Hg Te ][UI yielded the known ternary mercury
iodochalcogenide Hg [24]. Attempted syntheses of the
phosphorus or antimony variants of [Hg As ][UCl ], with the use
[
[
3
2
6
2ꢀ
no purely inorganic structure had contained the discrete [UCl
anion. The most closely related compounds are the alkali-metal
uranium chlorides, A UCl
(A ¼ Li, Na, Cs) [31,32], but in these
structures there are some A ꢄ ꢄ ꢄ CL interactions.
For [Hg Te ][UCl ], the formal oxidation states may be
6
]
4
2
2
3
2
6
2
6
4
4
2
3
2
6
]
3
2
6
3
2 2
Te I
assigned as +4, +2, ꢀ2, and ꢀ1 for U, Hg, Te, and Cl, respectively.
4
2
6
The interatomic distances listed in Table 2 are normal. The
of the same procedure but with elemental red P or Sb in place of
As, also failed.
˚
following comparisons can be made: U–Cl, 2.622(3)–2.624(3) A vs.
˚
˚ ˚
2
.621(7) A in Cs
in Hg Te Cl [26].
Although many types of mercury–arsenic frameworks are
known in the literature, [Hg As ][UCl ] appears to be a new
2 6
UCl [32]; Hg–Te, 2.664(1)–2.672(1) A vs. 2.644 A
3
2
2
3.2. Structures
4
2
6
[
Hg
3
Te
][MX
Te ][UCl
perpendicular to a* that form Hg
coordinate, with a linear geometry. The Te atoms are three-
coordinate, with a trigonal pyramidal geometry. The Hg Te rings
2
][UCl
6
] is isostructural with the known compounds
structure type. Its structure is shown in Fig. 3. All the Hg atoms are
[
Hg
3
Q
2
6
] (Q ¼ S, Se; M ¼ Zr, Hf; X ¼ Cl, Br) [7]. The structure
two-coordinate, with a linear geometry. The structure contains
2
2þ
2
1
of [Hg
3
2
6
] is shown in Fig. 1. It comprises ½Hg Te ꢁ layers
½Hg As
2
6 6
ꢁ layers along [010] that form Hg As rings. These adopt
1
3
2
3
6
Te
6
rings. The Hg atoms are two-
the twist-boat conformation, in contrast to the chair conformation
of the Hg Te rings in [Hg Te ][UCl ]. Unlike the Te atoms in
[Hg Te ][UCl ], which are three-coordinate, the As atoms are four-
coordinate with a distorted tetrahedral geometry. The As atoms in
each layer of the Hg As rings are connected by a Hg atom; this
results in a three-dimensional framework (Fig. 4). The Hg atoms
that link neighboring 2 ½Hg As
ꢁ layers result in the formation of
steps, as shown in Fig. 5. These steps contain repeat segments of
Hg As octagons, Hg As hexagons, and Hg As squares, all with
distorted geometries. Located between the ½Hg As ꢁ layers are
6
6
3
2
6
6
6
3
2
6
adopt the chair conformation (Fig. 2), as is seen in organic
2
1
2þ
molecules such as cyclohexane. Located between the ½Hg Te
ꢁ
6
6
3
2
2
ꢀ
layers are discrete [UCl
6
]
octahedra.
2
+
The [Hg
3
Q
2
] moiety is known to form various structural motifs
2
1
3
with one-, two-, or three-dimensional character.
b
-Hg
3
S
2
Br
2
[25]
has 11½Hg3S2 ꢁ zigzag chains in the [100] direction, with Br atoms
2þ
8
8
6
6
4
4
2
1
in the loops of each chain and between adjacent chains.
2
3
1
2þ
2ꢀ
[
Hg
3
Se
2
][Se
2
O
5
] exhibits ½Hg Se ꢁ stair-like chains in the [010]
discrete [UCl
[Hg As ][UCl
structural moiety. Previous compounds have most commonly
contained the [Hg As ] moiety, but other known structural
fragments include [Hg As ], [HgAs ], [Hg As ], [Hg11As ],
[Hg23As12], and [Hg13As As ] structural
2
moiety contain As–As bonding in the form of As dumbbells. This
6
]
octahedra.
1
3
3
2
2
2
+
direction. The compound
that extend in three directions.
a
-Hg
S
2
Cl
2
[26] contains [Hg
3
S
] chains
4
2
6
] is the first known example of the [Hg
4 2
As ]
The well-known hexachlorouranate(IV) octahedral anion
6
4
2
ꢀ
[
UCl
including [N(CH
-methyl-imidazolium [29], and [UCl
until the present discovery of [Hg Te
6
]
has been crystallized with a variety of countercations,
7
4
2
3
2
4
+
+
3
)
4
]
[27], [P(C
6
H
5
)
3
(C
((CH
][UCl
2
H
5
)] [28], 1-butyl-
8
]. All examples of the [Hg
6
4
2+
4ꢀ
3
2
3 2
)
SO)
6
]
[30]. However,
As ][UCl ],
3
2
6
] and [Hg
4
2
6
results in cavities of two different sizes within the cationic

ARTICLE IN PRESS
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D.E. Bugaris, J.A. Ibers / Journal of Solid State Chemistry 181 (2008) 3189–3193
arrangement in which the cavities are filled by an infinite chain of
ꢀ
corner-sharing [AgCl
and [Hg As ] [12] moieties also contain As
structures containing these species the cavities in the framework
3
]
tetrahedral anions. Both the [Hg
7
As
4
] [11]
4
ꢀ
3
2
2
dumbbells, but in
4+
are of equal size. There is no As–As bonding in the [Hg11As
cation of [Hg11As ][GaBr [14] so all As atoms may be assigned
an oxidation state of ꢀ3. Rather, there are ½Hg As
4
]
4
4 4
]
2
1
6
4
ꢁ layers with
6 6
As rings that are interconnected in the [001] direction
Hg
alternately by Hg
2
+
2+
3
2
and Hg
units. The [Hg23As12] [35] moiety
4
ꢀ
contains one As
cavities. The [Hg13As
per eight As atoms, and has nonequivalent cavities. The [Hg
motif in [Hg As] [CdI ] [15] is structurally the most similar to that
in the present [Hg As ][UCl ] structure. Neither compound has
As–As nor Hg–Hg bonding, and all cavities are identical. The key
difference is that [Hg As] [CdI ] (space group P2 ) has tetrahedral
anions in the cavities, whereas [Hg As ][UCl ] (space group P2 /c)
has octahedral anions in the cavities.
For [Hg As ][UCl ], the formal oxidation states may be
2
dumbbell per 12 As atoms and has equivalent
4ꢀ
2
8
] [35] moiety contains three As
dumbbells
As]
2
2
2
4
4
2
6
2
2
4
1
4
2
6
1
4
2
6
4 2 6
Fig. 3. The structure of [Hg As ][UCl ] viewed down [010].
assigned as +4, +2, ꢀ3, and ꢀ1 for U, Hg, As, and Cl, respectively.
The interatomic distances listed in Table 3 are normal. The
˚
following comparisons can be made: U–Cl, 2.605(3)–2.639(3) A vs.
˚
˚
2
2
.621(7) A in Cs
2
UCl
˚
6
[32]; Hg–As, 2.462(1)–2.480(1) A vs.
.491(1)–2.494(1) A in [Hg As ][TiCl ]Cl [10].
Although the mercury chalcohalides contain mercury-chalcogen
6
4
6
cationic moieties, there are also numerous examples of mercury-
chalcogen anionic moieties. Ternary compounds with an
alkali metal or alkaline-earth metal, mercury, and a chalcogen
contain mercury-chalcogen anionic structural motifs separated by
discrete alkali cations or alkaline-earth cations. The compounds
2ꢀ
Na
2
+
Hg
3
S
4
[36] and Rb
2
[Hg
3
Te
4
] [37] feature 2 ½Hg Q ꢁ layers with
1
3
4
+
Na or Rb cations between the layers. As another example, the
compound Rb [Hg (Te (Te Te [38] possesses
Hg ðTe Þ ðTe Þ Te ꢁ ribbons in the [010] direction separated
4
5
2
)
2
3
)
2
3
]
1
1
4ꢀ
½
5
+
2
2
3
2
3
by Rb cations.
Similarly, there are also some examples of mercury-pnictogen
anionic moieties. Ternary compounds of an alkali metal, mercury,
and a pnictogen (such as As) contain mercury-pnictogen anionic
structural motifs with alkali metal countercations. The compound
3 2
Fig. 4. Multiple [Hg As ] layers interconnected by Hg atoms. View is down [100].
KHgAs [39] features 2 ½HgAs ꢁ sheets of Hg
ꢀ
hexagons, with K
[HgAs ] [40],
anions separated by K
+
3 3
As
1
cations between the layers. Another example, K
4
2
4
ꢀ
+
contains discrete linear [As–Hg–As]
cations.
3.3. Magnetic susceptibility
[
Hg Te ][UCl ] exhibits a small magnetic susceptibility, which
3
2
6
is essentially independent of temperature between 60 and 400 K.
The average temperature-independent magnetic susceptibility
ꢀ
4
over the range 60–320 K is 25.4(4) ꢃ 10 emu/mol. This is similar
to the average temperature-independent magnetic susceptibilities
2
ꢀ
for other compounds containing the [UCl
6
]
anion, such as
ꢀ
4
ꢀ4
2
0.5(3) ꢃ 10 emu/mol for [PBuPh
emu/mol for [N(CH [UCl
Cs UCl [43].
The temperature-independent magnetic susceptibility of hex-
3
]
2
[UCl
6
] [41], 22.43 ꢃ10
Fig. 5. The steps in [Hg
4 2
As ][UCl
6 8 8
] containing repeated units of Hg As octagons,
ꢀ4
Hg As hexagons, and Hg
6
6
4
As
4
squares, all with distorted geometries.
3
)
4
]
2
6
] [42], and 24.4 ꢃ10 emu/mol for
2
6
framework. In most cases, such as [Hg
cavity is occupied by a metal of oxidation state +3. This metal is
6
As
4
][TiCl
6
]Cl [10], one
achlorouranate(IV) compounds has been explained [44] on the
basis of the perturbation of the ground-state electronic config-
3
ꢀ
4+
2
coordinated by six halogen atoms to form an octahedral [MX
anion. To balance the 4+ charge of the [Hg As ] moiety, the other
cavity is filled by a lone halogen anion. Less common is the
example of [Hg As ][FeBr ]Hg0.6 [33], in which the Fe atom has an
6
]
uration. U exhibits an f ground-state electronic configuration,
3
4+
6
4
4
with an H ground state for the free ion. Placing a U ion at the
body center of an octahedral configuration of six negative point
ꢀ
6
4
6
charges (Cl ligands) results in four symmetry representations
oxidation state of +2, so the charges of the cation and anion are
already balanced. The second cavity is partially filled by
(
G
1
,
G
3
,
G
4
, and
magnetic susceptibility will not be affected by the
states because they are not mixed with by the magnetic field.
G
5
). The singlet state,
G
1
, is lowest in energy. The
G
3
and
G
5
zerovalent mercury atoms. [Hg
6
As
4
][AgCl
3
]
2
[34] has a different
G
1

ARTICLE IN PRESS
D.E. Bugaris, J.A. Ibers / Journal of Solid State Chemistry 181 (2008) 3189–3193
3193
Therefore, the temperature-independent paramagnetism is due
solely to the ground state and the state lying E above it.
From tabulated values for the electronic levels, the temperature-
[4] J.A. Morkowski, A. Szajek, E. Talik, R. Troc, J. Alloys Compd. 443 (2007)
0–25.
2
G
1
G
4
D
[5] M.E. Kassner, D.E. Peterson, Phase Diagrams of Binary Actinide Alloys,
ASM International, Materials Park, 1995.
2
ꢀ
independent molar susceptibility for the [UCl
6
]
anion in Cs
2
UCl
6
[6] H. Puff, G. Lorbacher, D. Heine, Naturwissenschaften 56 (1969) 461.
7] J. Beck, S. Hedderich, J. Solid State Chem. 172 (2003) 12–16.
ꢀ
4
[
has been calculated [45] to be 26.7 ꢃ10 emu/mol, which agrees
ꢀ
4
[8] J.-P. Zou, G.-C. Guo, S.-P. Guo, Y.-B. Lu, K.-J. Wu, M.-S. Wang, J.-S. Huang, Dalton
Trans. 42 (2007) 4854–4858.
very well with the value of 25.4(4) ꢃ 10 emu/mol obtained here
for [Hg Te ][UCl ].
3
2
6
[9] A.V. Olenev, A.V. Shevelkov, J. Solid State Chem. 160 (2001) 88–92.
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Instruments, Inc., Madison, WI, USA, 2003.
[
[
3.4. Optical properties
[
[
The broad absorbance spectrum for [Hg
some intense absorption bands at 1.59, 1.84, 1.93, and 2.05 eV
whereas that for [Hg As ][UCl ] exhibits peaks at 1.58, 1.87, and
.93 eV (Supporting material). These absorbance peaks are
characteristic of f–f optical transitions, and the values correspond
3 2 6
Te ][UCl ] exhibits
[
[
[
4
2
6
1
2
ꢀ
well with those observed in other compounds with the [UCl
anion, including Cs UCl , [N(CH [UCl ], and [N(C [UCl
46,47]. Other compounds with uranium in the +4 oxidation state,
such as KU Se [48] and RbU SbS [49], also display f–f optical
6
]
[
[
2
6
3
)
4
]
2
6
2
H
5
)
4
]
2
6
]
[
2
6
2
8
[
[
19] Bruker, APEX2 Version 2.1-4, Bruker Analytical X-ray Instruments, Inc.,
Madison, WI, USA, 2006.
20] G.M. Sheldrick, Acta Crystallogr. Sect. A: Found. Crystallogr. 64 (2008)
112–122.
transitions in their absorbance spectra.
The band gaps for these compounds could not be determined
precisely because the absorption edges are obscured by inter-
[
[
21] L.M. Gelato, E. Parth e´ , J. Appl. Crystallogr. 20 (1987) 139–143.
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ference from the f–f optical transitions. However,
approximation from the spectra places the band gaps of
Hg Te ][UCl ] and [Hg As ][UCl ] around 2.6 and 1.9 eV, respec-
tively. A band gap of 2.6 eV for [Hg Te ][UCl ] is consistent with
the light-green color of the compound, and also with the band gap
of 2.63 eV determined for [Hg Se ][Se ] [8]. A band gap of 1.9 eV
for [Hg As ][UCl is consistent with the red color of the
a rough
[
3
2
6
4
2
6
3
2
6
[24] V.A. Lyakhovitskaya, N.I. Sorokina, A.A. Safonov, I.A. Verin, V.I. Andrianov,
Kristallografiya 34 (1989) 835–838.
3
2
2 5
O
[25] Y.V. Voroshilov, V.A. Khudolii, V.V. Pan’ko, Y.V. Minets, Inorg. Mater.
(Transl. Neorg. Mater.) 32 (1996) 1281–1286.
4
2
6
]
[
[
[
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compound, and also corresponds to the band gaps found by
diffuse reflectance spectroscopy for some similar compounds:
2
.05 eV for [Hg
6
As
4
][CdCl
6
]Hg0.5, 2.01 eV for [Hg
] [50].
6 4 6
As ][HgCl ]Hg0.5,
[29] S.I. Nikitenko, C. Hennig, M.S. Grigoriev, C. Le Naour, C. Cannes, D. Trubert,
E. Boss e´ , C. Berthon, P. Moisy, Polyhedron 26 (2007) 3136–3142.
and 1.94 eV for [Hg
6
As ][CdBr
4
6
[
30] G. Bombieri, K.W. Bagnall, J. Chem. Soc., Chem. Commun.
88–189.
[31] P.J. Bendall, A.N. Fitch, B.E.F. Fender, J. Appl. Crystallogr. 16 (1983) 164–170.
6 (1975)
1
Supporting material
[
[
32] T. Schleid, G. Meyer, L.R. Morss, J. Less-Common Met. 132 (1987) 69–77.
33] A.V. Olenev, O.S. Oleneva, M. Lindsj o¨ , L.A. Kloo, A.V. Shevelkov, Chem. Eur. J. 9
The absorbance spectra and the crystallographic files in CIF
format for [Hg Te ][UCl ] and [Hg As ][UCl ]. These latter files
(
2003) 3201–3208.
[34] O.S. Oleneva, A.V. Olenev, E.V. Dikarev, A.V. Shevelkov, Eur. J. Inorg. Chem. 20
2004) 4006–4010.
3
2
6
4
2
6
(
have been deposited with FIZ Karlsruhe as CSD numbers 419437
and 419438, respectively. These data may be obtained free of
charge by contacting FIZ Karlsruhe at +497247808 666 (fax) or
crysdata@fiz-karlsruhe.de (e-mail).
[
35] A.V. Olenev, A.V. Shevel’kov, B.A. Popovkin, Russ. J. Inorg. Chem. (Transl. Zh.
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[
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6
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[
[
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39] R. Vogel, H.-U. Schuster, Z. Naturforsch. B: Anorg. Chem. Org. Chem. 35 (1980)
114–116.
Acknowledgments
[
[
40] M. Asbrand, B. Eisenmann, M. Somer, Z. Kristallogr. New Cryst. Struct. 212
(1997) 79.
We thank Dr. George H. Chan and Prof. Richard P. Van Duyne
for help with the use of their single-crystal absorption spectro-
meter. This research was supported by the US Department of
Energy BES Grant ER-15522.
41] J.P. Day, L.M. Venanzi, J. Chem. Soc. A 2 (1966) 197–200.
[42] G.A. Candela, C.A. Hutchison Jr., W.B. Lewis, J. Chem. Phys. 30 (1959)
46–250.
2
[
[
[
[
[
[
43] B.N. Figgis, D.J. Mackey, Aust. J. Chem. 27 (1974) 2053–2055.
44] C.A. Hutchison Jr., G.A. Candela, J. Chem. Phys. 27 (1957) 707–710.
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