Two new compounds, Β-ScTe and Y3Au2, and a reassessment of Y2Au

Article abstract of DOI:10.1107/S010827011103589X

Two new compounds, Β-ScTe (scandium telluride) and Y ₃Au₂ (triyttrium digold), have been synthesized by high-temperature solid-state techniques and their crystal structures, along with that of Y₂Au (diyttrium gold), have been refined by single-crystal X-ray diffraction methods. Β-ScTe is a superstructure of ScTe (NiAs-type), featuring double hexa-gonal close-packed layers of Te atoms with the octa-hedral cavities filled by Sc atoms. Y₃Au₂ displays a U ₃Si₂-type structure and is built from Au ₂-centered bitrigonal prisms and centered cubes of Y atoms. The structure of Y₂Au is better described as an inverse PbCl ₂-type structure rather than a Co₂Si-type.

Full text of DOI:10.1107/S010827011103589X

inorganic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
Two new compounds, b-ScTe and
Y Au , and a reassessment of Y Au
3
2
2
Ping Chai and John D. Corbett*
Department of Chemistry, Iowa State University, Ames, IA 50010, USA
Correspondence e-mail: jcorbett@iastate.edu
Received 27 July 2011
Accepted 2 September 2011
Online 31 October 2011
Two new compounds, ꢀ-ScTe (scandium telluride) and Y Au2
3
(triyttrium digold), have been synthesized by high-tempera-
ture solid-state techniques and their crystal structures, along
with that of Y Au (diyttrium gold), have been refined by
2
single-crystal X-ray diffraction methods. ꢀ-ScTe is a super-
structure of ScTe (NiAs-type), featuring double hexagonal
close-packed layers of Te atoms with the octahedral cavities
filled by Sc atoms. Y Au displays a U Si -type structure and is
Figure 1
a) A view of one unit cell, approximately along [001]. (b) A section of
-ScTe, approximately along [100].
(
ꢀ
3
2
3
2
built from Au -centered bitrigonal prisms and centered cubes
2
approximately along [100] is shown in Fig. 1(b), in which Te
atoms form hexagonal close-packed (hcp) layers with
ABAC . . . stacking, leaving all nominal octahedral cavities
filled by Sc atoms. Note that ScTe (NiAs-type) crystallizes in
of Y atoms. The structure of Y Au is better described as an
2
inverse PbCl -type structure rather than a Co Si-type.
2
2
Comment
˚
the same space group, P6 /mmc, with a = 4.130 (5) A and c =
3
˚
6.749 (5) A, and contains simple hcp Te atoms of ABAB . . .
Research within solid-state chemistry on ternary and polynary
compounds has attracted much attention during the past few
decades because of their interesting structures, bonding and
physical properties. Knowledge of binary compounds can
provide significant references during the exploratory synthesis
of polynary compounds, and their identification is therefore
valued. Although many binary combinations of elements are
covered by binary phase diagrams and the crystal databases,
some have been missed because of the limitations of the
earlier experiments. For instance, only two compounds, viz.
ScTe and Sc Te , were in the Sc–Te phase diagram reported in
ordering with Sc atoms occupying the octahedral cavities
(Men kov et al., 1961). Therefore, ꢀ-ScTe is a stacking variant
of ScTe, with a c axis twice as large.
Y Au crystallizes in the U Si -type structure in the space
3
2
3
2
group P4/mbm (No. 127). An approximately [001] projection
˚
along the short 3.907 (3) A c axis is shown in Fig. 2. The basic
building units are an Au -centered bitrigonal prism (BTP) of
2
2
3
1990 (Okamoto, 1990), missing several examples, Sc Te, Sc Te
and Sc Te , which were discovered later during the study of
2 8 3
9
2
ternary systems (Maggard & Corbett, 1997, 1998, 2000). We
discovered that the structure of ꢀ-ScTe was still missing, with
an inverse Li O -type structure, a double hexagonal close-
2
2
packed (dhcp) version of ScTe (NiAs-type) (Men kov et al.,
961). Y Au was missed in the investigation of the Y–Au
phase diagram (Saccone et al., 1997), whereas Y Au was
1
3
2
2
identified as Co Si-type (Yakinthos et al., 1978) from lattice
2
parameters only; no refinement of powder diffraction inten-
sities was carried out. The crystal structures of these three
phases are described here.
ꢀ-ScTe is presumably a high-temperature phase with an
inverse Li O -type structure. A view of the unit cell approxi-
mately along [001] is shown in Fig. 1(a) and a section
2
2
Figure 2
A projection of Y
3 2
Au , approximately along [001].
Acta Cryst. (2011). C67, i53–i55
doi:10.1107/S010827011103589X
# 2011 International Union of Crystallography i53

inorganic compounds
ScTe
Crystal data
ScTe
Z = 4
Mo Kꢁ radiation
ꢂ = 17.64 mm
T = 293 K
M
r
= 172.56
À1
Hexagonal, P6 =mmc
a = 4.0969 (6) A
c = 13.602 (3) A
˚
V = 197.71 (6) A
3
˚
˚
0.15 Â 0.08 Â 0.07 mm
3
Data collection
Bruker SMART CCD area-detector
diffractometer
Absorption correction: multi-scan
1274 measured reflections
92 independent reflections
90 reflections with I > 2ꢃ(I)
(
T
SADABS; Sheldrick, 1996)
min = 0.177, Tmax = 0.372
Rint = 0.020
Refinement
2
2
R[F > 2ꢃ(F )] = 0.036
wR(F ) = 0.081
8 parameters
˚
À3
ꢀꢄmax = 1.21 e A
2
ꢀꢄmin = À1.65 e A˚
À3
S = 1.57
92 reflections
Figure 3
2
A view of Y Au, approximately along [001].
Y3Au2
Y2 atoms and a Y1-centered Y2 cube. The Au unit is an
2
˚
unusual dimer 3.0539 (19) A long. The two-dimensional motif
Crystal data
is created in such a way that each Y2 cube, with the centered
Y1 atom on a fourfold axis, interconnects with four identical
units through shared Y2–Y2 edges, leaving the cavities filled
by the BTPs. The centered Y1 and Au1 atoms lie on a mirror
plane at c = 0. The two-dimensional motif repeats along c to
form a three-dimensional network, sharing bitriangular and
square faces.
Y Au2
3
Z = 2
Mo Kꢁ radiation
ꢂ = 91.35 mm
T = 293 K
M
r
= 660.66
À1
Tetragonal, P4=mbm
a = 8.059 (3) A
c = 3.907 (3) A
˚
V = 253.7 (3) A
˚
˚
0.05 Â 0.04 Â 0.02 mm
3
Data collection
Bruker SMART CCD area-detector
diffractometer
Absorption correction: multi-scan
1866 measured reflections
194 independent reflections
156 reflections with I > 2ꢃ(I)
The structure of Y Au in the space group Pnma projected
2
along [010] is shown in Fig. 3, in which each Au atom forms the
center of a trigonal prism (TP) of Y1 or Y2 atoms that shares
trigonal faces with identical units to generate an infinite one-
dimensional column along b. The TPs interconnect with
shared Y2–Y2 edges and lead to the formation of puckered
sheets along a. Adjoining sheets stack along c, with displace-
ments of b/2, to create a three-dimensional structural network.
As a result, each TP is tricapped by two Y1 atoms and one Y2
(
T
SADABS; Sheldrick, 1996)
min = 0.092, Tmax = 0.262
Rint = 0.093
Refinement
2
2
R[F > 2ꢃ(F )] = 0.030
wR(F ) = 0.069
11 parameters
˚
À3
ꢀꢄmax = 1.46 e A
ꢀꢄmin = À1.40 e A˚
2
À3
S = 0.93
194 reflections
atom so that each Au atom has nine neighbors. Y Au is better
2
Y2Au
described as an inverse PbCl -type structure rather than the
2
earlier reported Co Si-type, in which the Si atom would have
2
ten neighbors (Flahaut & Th e´ vet, 1980; Liu & Corbett, 2006).
Crystal data
˚
V = 312.7 (2) A
3
Y
2
Au
= 374.79
M
r
Z = 4
Mo Kꢁ radiation
ꢂ = 83.29 mm
T = 293 K
Orthorhombic, Pnma
˚
À1
Experimental
a = 7.115 (3) A
˚
b = 4.933 (2) A
˚
c = 8.908 (4) A
The formation of all three phases was in fact first noted in powder
pattern data from nearby ternary systems. ꢀ-ScTe was synthesized
0.12 Â 0.08 Â 0.04 mm
from a mixture of Sc and Sc
prereaction of Sc and Te in a 2:3 ratio, sealed in a silica tube under
vacuum, heated at 723 K for 12 h and then at 1173 K for 72 h. Y Au
and Y Au were prepared from mixtures of high-purity elements. The
2
Te
3
. The latter was obtained from a
Data collection
Bruker SMART CCD area-detector
diffractometer
Absorption correction: multi-scan
1619 measured reflections
345 independent reflections
299 reflections with I > 2ꢃ(I)
3
2
2
(
T
SADABS; Sheldrick, 1996)
min = 0.036, Tmax = 0.135
Rint = 0.039
three combinations were each pelletized and arc-melted under an
argon atmosphere in a glove-box. The pellets were then sealed in
tantalum containers and annealed in a graphite-heated vacuum
furnace at 1573 K for 200 h for ꢀ-ScTe, and at 1323 K for one week
Refinement
2
2
R[F > 2ꢃ(F )] = 0.026
wR(F ) = 0.058
20 parameters
˚
À3
ꢀꢄmax = 1.76 e A
for Y Au and Y Au. The products were crushed with the aid of an
agate mortar into small crystals that were suitable for single-crystal
X-ray diffraction.
3
2
2
2
ꢀꢄmin = À2.14 e A˚
À3
S = 1.07
345 reflections
ꢀ
i54 Chai and Corbett
3
ScTe, Y Au
2
and Y
2
Au
Acta Cryst. (2011). C67, i53–i55

inorganic compounds
For all three title compounds, data collection: SMART
Bruker, 2002); cell refinement: SAINT-Plus (Bruker, 2003); data
References
(
Brandenburg, K. (2000). DIAMOND. Crystal Impact GbR, Bonn, Germany.
Bruker (2002). SMART for Windows NT/2000. Version 5.630. Bruker AXS
Inc., Madison, Wisconsin, USA.
Bruker (2003). SAINT-Plus. Version 6.45. Bruker AXS Inc., Madison,
Wisconsin, USA.
Flahaut, J. & Th e´ vet, F. (1980). J. Solid State Chem. 32, 365–372.
Liu, S. F. & Corbett, J. D. (2006). J. Solid State Chem. 179, 830–835.
Maggard, P. A. & Corbett, J. D. (1997). Angew. Chem. Int. Ed. Engl. 18, 1974–1976.
Maggard, P. A. & Corbett, J. D. (1998). Inorg. Chem. 37, 814–820.
Maggard, P. A. & Corbett, J. D. (2000). J. Am. Chem. Soc. 122, 838–843.
Men kov, A. A., Komissarova, L. N. & Simonav, Ju. P. (1961). Dokl. Akad.
Nauk SSSR, 141, 364–367.
Okamoto, H. (1990). Sc–Te (Scandium–Tellurium), Binary Alloy Phase
Diagrams, 2nd ed., Vol. 3, edited by T. B. Massalski, pp. 3329–3330.
Materials Park, OH, USA: ASM International.
reduction: SAINT-Plus; program(s) used to solve structure:
SHELXTL (Sheldrick, 2008); program(s) used to refine struc-
ture: SHELXTL; molecular graphics: DIAMOND (Brandenburg,
2000); software used to prepare material for publication:
SHELXTL.
This research was supported by the US National Science
Foundation, Solid State Chemistry. All of the work was
performed using the facilities of the Ames Laboratory, US
Department of Energy.
Saccone, A., Delfino, S., Maccio, D. & Ferro, R. (1997). J. Chim. Phys. Phys.
Chim. Biol. 94, 948–957.
Sheldrick, G. M. (1996). SADABS. University of G o¨ ttingen, Germany.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.
Yakinthos, J. K., Ikonomou, P. F. & Anagnostopoulos, T. (1978). J. Magn.
Magn. Mater. 8, 308–312.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: FN3086). Services for accessing these data are
described at the back of the journal.
ꢀ
Acta Cryst. (2011). C67, i53–i55
Chai and Corbett
ScTe, Y
Au
3 2
2
and Y Au i55