Er17Ru6Te3: A highly condensed metal-rich ternary telluride

Article abstract of DOI:10.1016/j.jssc.2008.01.034

Er₁₇Ru₆Te₃ is obtained from high-temperature solid-state reactions in tantalum ampoules. The structure according to single-crystal X-ray diffraction is monoclinic, C2/m (no. 12), Z=4, a=40.185(8) A, b=3.9969(8) A, c=16.037(3) A, β=95.12(3)°, V=2565.5(9) A³. The condensed structure consists of a complex intermetallic network of intergrown sheets of edge-sharing tetrakaidecahedra (tricapped trigonal prisms, TCTP), and pairs of rectangular-face-sharing bicapped trigonal prisms (BCTP) built of erbium and centered by ruthenium. This array also contains isolated columns of TCTP erbium normal to these sheets that contain tellurium. Basal face sharing of all Er polyhedra along the short b-axis gives rise to the three-dimensional network. Synthesis and the crystal structure of the compound are discussed.

Full text of DOI:10.1016/j.jssc.2008.01.034

ARTICLE IN PRESS
Journal of Solid State Chemistry 181 (2008) 871–877
www.elsevier.com/locate/jssc
Er17Ru6Te3: A highly condensed metal-rich ternary telluride
Ã
Akash Mehta, John D. Corbett
Department of Chemistry, Iowa State University, Ames, IA 50011-3020, USA
Received 10 August 2007; received in revised form 9 January 2008; accepted 19 January 2008
Available online 5 February 2008
Abstract
Er17Ru6Te3 is obtained from high-temperature solid-state reactions in tantalum ampoules. The structure according to single-crystal
3
˚
˚
˚
˚
X-ray diffraction is monoclinic, C2/m (no. 12), Z ¼ 4, a ¼ 40.185(8) A, b ¼ 3.9969(8) A, c ¼ 16.037(3) A, b ¼ 95.12(3)1, V ¼ 2565.5(9) A .
The condensed structure consists of a complex intermetallic network of intergrown sheets of edge-sharing tetrakaidecahedra (tricapped
trigonal prisms, TCTP), and pairs of rectangular-face-sharing bicapped trigonal prisms (BCTP) built of erbium and centered by
ruthenium. This array also contains isolated columns of TCTP erbium normal to these sheets that contain tellurium. Basal face sharing
of all Er polyhedra along the short b-axis gives rise to the three-dimensional network. Synthesis and the crystal structure of the
compound are discussed.
r 2008 Published by Elsevier Inc.
Keywords: Metal-rich compounds; Electron-poor phases; Tellurides; Crystal structure; Tricapped trigonal prisms; Erbium ruthenium telluride
1. Introduction
chemistry has been extended [11] to ternary compounds of
the electron-poorer rare-earth metal (R) telluride systems
and to the realization of many new compounds with novel
compositions, structures, and properties. These include the
hexagonal Fe2P-type derivatives Dy6ZTe2 (Z ¼ Fe–Ni)
[12], Sc6ZTe2 (Z ¼ Ru, Os, Rh, Ir) [13], Sc6ZTe2
(Z ¼ Mn–Ni) [14] as well as the orthorhombic Sc6ZTe2
(Z ¼ Cu, Ag, Cd) [15], Sc6PdTe2 [16], R6ZTe2 (R ¼ Y;
Z ¼ Y, Rh, Pd, Ag; R ¼ Lu; Z ¼ Cu, Ag) [17]. The last
group can be viewed as derivatives (through substitution of
Z for Te) of the binary Sc2Te-type [18] structure also known
for Dy2Te and Gd2Te [19]. The collection of structures
reflect strong heterometallic interactions between the rare-
earth and late transition metals, including many 4d and 5d
members in the latter role, evidently a key factor in their
stabilization. (Still, it is important to remember that such
‘stabilities’ (or not) are always relative to the stability of
alternate phases at that particular composition.)
Exploration for new materials, an important step in
solid-state chemistry, has led to the discovery of many
compounds with diverse properties and to better under-
standing of structure, bonding, and what is possible in the
solid state. Exploratory research in rare-earth-metal tell-
uride chemistry has been pursued with the principal
objective of expanding the boundaries for the relatively
electron-poor, metal-rich systems [1]. Earlier synthetic
explorations of ternary metal-rich chalcogenides, which
similarly focused on the lighter chalcogenides of the
early–late pairs of transition metals [2], revealed many
new and novel phases, for example, Ta8NiSe8 [3], Hf8ZTe6
(Z ¼ Mn–Fe) [4], Ta11Z2Se8 (Z ¼ Fe–Ni) [5], Hf5FeTe3 [6],
Zr6ZTe2 (Z ¼ Mn–Ni, Ru, Pt) [7], Ta9Z2S6 (Z ¼ Fe–Ni)
[8], and Nb6ZS2 (Z ¼ Fe–Ni) [9]. These investigations took
advantage of the considerable stabilization of mixed
early–late transition metal bonding that occurs in such
polar intermetallics, effects that Brewer and Wengert
attributed to Lewis acid–baselike donation of electrons
from the late to the earlier transition metal [10]. This sort of
Explorations of ternary transition-metal systems have
been very productive. Many of the recently reported metal-
rich chalcogenides have common structural motifs of
tetrakaidecahedra (tricapped trigonal prisms, TCTP) of
the earlier metal centered by a later transition metal (see
[20]). With TCTP as fundamental building blocks, different
structures can be constructed via different modes of
Ã
Corresponding author. Fax: +1 515 294 6789.
E-mail address: jcorbett@iastate.edu (J.D. Corbett).
0022-4596/$ - see front matter r 2008 Published by Elsevier Inc.
doi:10.1016/j.jssc.2008.01.034

ARTICLE IN PRESS
A. Mehta, J.D. Corbett / Journal of Solid State Chemistry 181 (2008) 871–877
872
condensation, e.g., in the tellurides, R6ZTe2 (R ¼ Gd, Er,
Z ¼ Co, Ni, Ru [21]; R ¼ Sc, Z ¼ Ru, Rh, Ir, Os [13])
versus R7Z2Te2 (R ¼ Er, Z ¼ Ni [22]; R ¼ Lu, Z ¼ Ni, Pd,
Ru [23]). Others contain fundamental building units of
infinite, puckered chains of rare-earth metals in six rings
that sandwich later transition metals, for example, R5Z2Te2
(R ¼ Sc, Z ¼ Ni [24]; R ¼ Y, Z ¼ Fe, Co, Ni [25]; R ¼ Er,
Z ¼ Co, Ni [26]. Both groups can be related to the parent
compound Gd3MnI3 [27]. Here we report Er17Ru6Te3; in
which waist-capped Er6Ru trigonal prisms play a dominant
structural role. The compound has the highest rare-earth-
metal to tellurium ratio after Lu8Te and Lu7Te [28].
Huber Guinier 670 image-plate diffractometer and Cu Ka1
radiation. Samples were first ground to a fine powder and
evenly distributed between two Mylar films. These were
then mounted between Al-rings in the glove box for
protection against air and moisture.
2.3. Single-crystal X-ray diffraction
Thin plate-shaped black crystals were mounted inside
0.3-mm i.d. thin-walled glass capillaries in an Ar-filled
glove box, and these were first closed vacuum grease and
then later flame sealed outside of the box. Data collections
were made with the aid of a Bruker APEX CCD-based
X-ray diffractometer over a sphere of reciprocal space to
2ymax ¼ 56.61 with 10 s/frame exposures. The reflection
intensities were integrated with SAINTPLUS 6.22 [29]
subprogram, and absorption effects were corrected by
means of SADABS [30]. The reflection condition h+k ¼ 2n
for the monoclinic cell indicated a C-centered cell, the
mean value of |E2–1| ¼ 1.167 strongly suggested centro-
symmetry, and the space group C2/m (no. 12) was chosen.
The structure was solved by direct methods and refined on
F2 with the aid of SHELXTL 6.10 [31]. The final
anisotropic refinement converged at R1 ¼ 0.0510, wR2 ¼
0.1401 for I42s(I). The largestꢀFourier difference map
2. Experimental section
2.1. Syntheses
Owing to the high sensitivity of several components of the
Er–Ru–Te systems toward air and moisture, all manipula-
tions were performed inside He- or N2-filled glove boxes.
The elements were used as received: Er metal (99.995 at%
total, Ames Laboratory), Ru metal (99.95%, Ames Labora-
tory), Te (99.99%, Aldrich), all as chunks. The synthesis of
Er17Ru6Te3 began with the preparation of ErTe, for which
the elements in a 1:1 molar ratio were sealed inside a silica
tube under high vacuum. This was slowly heated to 450 1C,
held for 2 days, heated at 750 1C for 3 days, and then
radiatively cooled. The product ErTe (495% yield) (NaCl-
type structure) was single phase according to powder X-ray
diffraction, and no sign of side reactions with the walls of
the silica was visible. The mixed components ErTe, Er, and
Ru in 7:2:2 proportions were pressed into a 5 mm pellet with
a hydraulic press inside the glove box. This was arc-melted
at 30A for 30s/side inside an Ar-filled glove box to give a
shining button with a weight loss of around 2 wt%. The
button wrapped in Mo foil was loaded into a 9-mm i.d.
tantalum tube welded at one end, the other end of the tube
was crimped shut inside the glove box, and the tube was
transferred to an Ar-filled arc-welder and sealed. The tube
was mounted inside a graphite-heated high vacuum furnace
(Labmaster Thermal Technology Inc. 1000-2560-FP20),
which was first evacuated for 1 day under high vacuum
(10ꢀ7 Torr). The button was then sintered at 12501C for 2
weeks, cooled to 700 1C at 101C/h, and then allowed to cool
radiatively. Its X-ray diffraction powder pattern showed
what was subsequently found to be Er17Ru6Te3 in 460%
yield, with ErTe as the other major phase. After the
structure and composition had been determined, a compar-
able reaction of a 17:6:3 Er:Ru:Te composition gave
Er17Ru6Te3 in 490% yield, plus a slight trace of ErTe.
The powdered compound decomposes within an hour upon
exposure to moist air at room temperature.
3
˚
residuals, 10.722 and ꢀ4.817 e /A , located 1.16 and
˚
1.27 A from Te1 and Te2, respectively, resulted from
inadequate absorption corrections. An alternative, transi-
tion metal–Te mixing has never been observed in such
ternary rare-earth-metal compounds, and variations in
lattice constants with altered synthetic compositions that
would suggest a range were not observed in this system
either. Some crystal and refinement parameters are
summarized in Table 1 and the positional data given in
Table 2 have been reduced to the standard settings with
TIDY [32]. The unit cell parameters listed in Table 1, and
the nearest-neighbor distances given in Table 3 have been
obtained with the use of lattice dimensions from Guinier
X-ray powder diffraction.
3. Results and discussion
3.1. Synthesis
Synthesis of Er17Ru6Te3 was similar to that of earlier
reported Er6RuTe2 [21]. The present compound was
obtained in 490% from a suitable Er, Ru, ErTe mixture
that had been arc-melted and then equilibrated for 2 weeks
at 1250 1C. This compares with the evident synthesis of
Er6RuTe2 in a 80–90% yield directly from a mixture of
Er3Ru (made by arc-melting Er and Ru) with Er2Te3 at
1000 1C for 10 days without further arc-melting [21]. Both
processes are intended to shorten diffusion path lengths
and thus to give more rapid reactions between certain
combinations of the reactants. As above, prior arc-melting
of the reactants has proven to be useful in the synthesis of
Lu8Te [28] (followed by 1000 1C for 2 weeks), Lu7Z2Te2
2.2. Powder X-ray diffraction
Powder diffraction patterns were recorded in the 2y
range of 4–1001 over a period of 60 min with the aid of a

ARTICLE IN PRESS
A. Mehta, J.D. Corbett / Journal of Solid State Chemistry 181 (2008) 871–877
873
Table 1
Crystallographic and refinement data for Er17Ru6Te3
Table 2
Atomic coordinates and equivalent isotropic displacement parameters
2
3
˚
(A ꢂ 10 ) for Er17Ru6Te3
Formula mass (amu)
Space group
3832.6
C2/m (no. 12)
b,c
U(eq)
Atom
Wyck sym.
Site sym.
xa
z
Unit-cell dimensionsa (A,
˚
3
deg, A )
˚
Er1
Er2
4i
4i
4i
4i
4i
4i
4i
4i
2a
2c
4i
4i
4i
4i
4i
4i
4i
4i
4i
4i
4i
4i
4i
4i
4i
4i
4i
m
m
m
m
m
m
m
m
2/m
2/m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
0.7020(1)
0.2695(1)
0.2681(1)
0.3037(1)
0.1770(1)
0.1311(1)
0.1851(1)
0.0903(1)
0
0.1253(1)
0.0716(1)
0.5858(1)
0.3984(1)
0.2917(1)
0.5971(1)
0.7809(1)
0.2680(1)
0
12(1)
11(1)
14(1)
12(1)
10(1)
8(1)
a
40.185(8)
3.9969(8)
Er3
Er4
b
c
16.037(3)
95.12(3)
2565.5(9)
Er5
Er6
b
Volume
Er7
Er8
12(1)
7(1)
Z
4
9.923
dcalc (Mg/m3)
Temperature (K)
Crystal dimensions (mm)
Radiation
Er9
13(1)
14(1)
13(1)
11(1)
12(1)
7(1)
293(2)
0.3 ꢂ 0.1 ꢂ 0.1
Er10
Er11
Er12
Er13
Er14
Er15
Er16
Er17
Er18
Ru1
Ru2
Ru3
Ru4
Ru5
Ru6
Te1
0
0.5000
0.3563(1)
0.4720(1)
0.4411(1)
0.0935(1)
0.5260(1)
0.1337(1)
0.3618(1)
0.5588(1)
0.8085(1)
0.1884(1)
0.3620(1)
0.0233(1)
0.0252(1)
0.6347(1)
0.2499(1)
0.0740(1)
0.9240(1)
0.0781(1)
0.1627(1)
0.3888(1)
0.7716(1)
0.3347(1)
0.0963(1)
0.5778(1)
0.1093(1)
0.0070(1)
0.4786(1)
0.2770(1)
0.1897(1)
0.6928(1)
0.2207(1)
0.2529(1)
0.4539(1)
0.0448(1)
Graphite monochromated Mo Ka,
˚
l ¼ 0.71073 A
y Range for data collection
Index ranges
1.02–28.301
ꢀ51o ¼ ho ¼ 51, ꢀ5o ¼ ko ¼ 5,
11(1)
7(1)
ꢀ21o ¼ lo ¼ 21
Completeness for
94.4
13(1)
12(1)
7(1)
theta ¼ 28.301, %
Reflections collected, R(int)
Obs. indep. reflections
[I42s(I)]
11181, 0.0824
3439
8(1)
7(1)
Data/restraints/parameters
Absorption coeff. (MoKa)
3439/0/160
61.620
6(1)
6(1)
(mmꢀ1
F(0 0 0)
)
7(1)
6304
SADABS
1.059
11(1)
4(1)
5(1)
Absorption correction
Goodness-of-fit on F2
R1, wR2 [I42s(I)]
(all data)
Te2
Te3
0.0510, 0.1401
0.0597, 0.1451
10.72, ꢀ4.82
ay=0 for all atoms.
bU(eq) is defined as one-third of the trace of the orthogonalized Uij
Largest diff. peak and hole
ꢀ
3
(e /A )
˚
tensor.
cAnisotropic displacement parameters appear in the cif file–see
Supplementary data.
a
˚
From Guinier data obtained with CuKa radiation (l ¼ 1.54050 A) at
293 K.
[23] (Z ¼ Ni, Pd, Ru; 1200 1C for 2 days), and Lu11Te4 [33]
(1300 1C for 2 days). Nonetheless, the refractory nature of
these particular R, Z metals evidently may still afford some
hindrance to reaction and, as before [34], their prior
reaction to form a binary intermetallic, Er3Ru, for
example, clearly seems to be helpful in reducing the time
and temperatures necessary to gain good yields of single
crystals.
lar-face-sharing bicapped trigonal prisms (BCTP)2,
Fig. 2b. Both share trigonal basal faces along the b-axis
to generate the infinite three-dimensional structure. The
common bifunctional character of the Er atoms in many
edge-sharing TCTP—prismatic in one cluster and face
capping in the next—gives rise to a corrugation of the
prisms pairs in the a–b plane, as can be seen in Fig. 1b.
The Er–Er, Er–Ru, and Er–Te bond distances (Table 3)
in Er17Ru6Te3 are comparable to those observed in other
ternary tellurides of late rare-earth and heavy transition
metals, for example, in R6ZTe2 [17,21] (R=Y, Gd, Er;
Z=Ru, Rh, Pd) and R7Z2Te2 [23] (R ¼ Lu; Z ¼ Pd, Ru).
The Er TCTP surroundings about most Ru generally
3.2. Structure
The large ratio of metal to tellurium in this compound
means a high degree of condensation is present, the Ru
being characteristically centered in TCTP of Er. Fig. 1
shows about one-half (a/2) of a near-[010] section of the
˚
consist of six close and three ꢁ0.3 A more distant Er
neighbors, corresponding to the trigonal prismatic and the
face-capping dispositions, respectively. However, a few of
˚
monoclinic Er17Ru6Te3 (C2/m) along the short (ꢁ4.00 A)
˚
the secondary Er–Ru values are as much as 0.5–0.6 A
b-axis. (A labeled view of the complete cell is available in
Supporting data.) The relatively few Te atoms are located
in isolated columns that run through the structure along b,
but representations of their bonding to the surrounding Er
are not marked. The metal atom part of the structure is
made up of two types of Er-based, Ru-centered building
blocks: TCTP (tetrakaidecahedra), Fig. 2a, and rectangu-
longer because of distortions necessary in fitting the TCTP
and BCTP into this rather complex array. Of course, Ru in
the BCTP dimers is only eight-bonded to Er, and this leads
to shorter face-capping Ru–Er interactions on the back
side. Interestingly, the Er–Te distance distribution is nearly
reversed from that of Er–Ru, for the following reasons:

ARTICLE IN PRESS
A. Mehta, J.D. Corbett / Journal of Solid State Chemistry 181 (2008) 871–877
874
Table 3
Bond distances (A) for Er17Ru6Te3
˚
Atom 1
Er1
Atom 2
ꢂ
Distance
Atom 1
Er9
Atom 2
ꢂ
Distance
Atom 1
Er18
Atom 2
ꢂ
Distance
Ru1
Ru6
Te1
Er16
Er2
2
2.918(1)
3.224(3)
3.344(1)
3.394(1)
3.455(1)
3.537(1)
3.550(1)
2.796(1)
3.078(2)
3.273(3)
3.329(2)
3.455(2)
3.482(2)
3.487(1)
3.537(1)
2.902(1)
3.399(1)
3.442(2)
3.457(1)
3.497(3)
3.540(1)
3.601(2)
3.775(1)
2.807(1)
3.036(2)
3.176(3)
3.290(1)
3.540(1)
3.539(2)
3.562(1)
2.798(1)
2.991(2)
3.051(2)
3.373(1)
3.444(1)
3.457(1)
3.470(1)
3.550(1)
2.837(1)
3.098(2)
3.115(2)
3.290(1)
3.296(1)
3.477(1)
3.500(2)
3.547(1)
2.849(1)
3.372(1)
3.389(3)
3.487(1)
3.500(2)
3.542(1)
3.562(1)
3.664(2)
2.828(1)
2.868(2)
3.107(1)
3.389(1)
3.392(1)
3.468(2)
3.509(1)
3.601(1)
Ru4
Te3
2
3.102(2)
3.200(1)
3.450(1)
3.548(1)
3.128(1)
3.167(2)
3.467(1)
3.550(1)
2.931(1)
3.177(2)
3.453(1)
3.482(1)
3.490(1)
3.542(1)
3.604(1)
3.844(1)
2.874(1)
3.055(1)
3.263(1)
3.352(1)
3.542(1)
3.548(1)
3.663(2)
3.937(1)
2.803(1)
3.317(1)
3.451(1)
3.467(1)
3.508(3)
3.547(1)
3.592(1)
3.937(1)
2.835(1)
2.918(2)
3.088(1)
3.296(2)
3.451(1)
3.542(1)
3.604(1)
3.664(2)
2.873(1)
3.061(1)
3.274(1)
3.352(2)
3.509(1)
3.550(1)
3.592(1)
3.958(1)
2.822(1)
2.970(2)
3.091(2)
3.389(1)
3.394(1)
3.444(1)
3.490(1)
3.635(1)
2.924(1)
3.221(2)
3.339(1)
3.373(1)
3.477(1)
3.539(1)
Er8
Er3
2
3.601(1)
3.775(1)
2.833(1)
3.299(1)
3.392(1)
3.396(3)
3.450(1)
3.635(1)
3.663(2)
3.958(1)
2.796(1)
2.918(1)
2.931(2)
2.970(2)
3.273(3)
3.389(3)
2.807(1)
2.902(1)
2.924(1)
2.991(1)
3.115(1)
3.497(1)
2.835(1)
2.837(1)
2.849(1)
3.176(1)
3.177(1)
3.508(1)
2.833(1)
2.868(1)
2.874(1)
3.061(1)
3.102(1)
2.803(1)
2.873(1)
2.918(1)
3.055(1)
3.167(1)
2.798(1)
2.822(1)
2.828(1)
3.224(1)
3.221(2)
3.396(1)
3.036(1)
3.051(1)
3.078(1)
3.344(1)
3.372(1)
3.399(1)
3.098(1)
3.107(1)
3.128(1)
3.274(1)
3.317(1)
3.339(1)
3.088(2)
3.091(2)
3.200(1)
3.263(1)
3.299(1)
3.453(1)
1
2
2
1
2
2
2
1
1
2
1
1
2
2
2
2
2
1
1
2
2
1
3
1
1
2
2
1
2
2
1
1
2
1
2
1
2
2
1
1
2
1
2
1
2
2
2
1
2
1
2
2
1
2
1
1
1
2
1
2
2
2
4
4
2
2
4
4
2
1
2
1
2
2
2
1
2
2
2
1
2
2
1
1
2
2
2
2
1
2
1
1
2
1
1
1
2
2
2
1
2
2
2
1
2
2
1
1
2
1
1
1
2
1
2
2
2
1
2
2
2
1
1
2
2
2
1
2
2
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
1
2
2
1
2
2
1
2
1
2
2
2
1
1
1
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
Er18
Er12
Te2
Ru4
Te3
Er10
Er11
Er8
Er2
Er5
Ru5
Er13
Er15
Ru1
Ru3
Te3
Ru6
Er9
Er2
Ru1
Te1
Ru1
Er2
Er16
Er12
Er15
Er2
Ru1
Ru2
Ru3
Er1
Er2
Er1
Er11
Er7
Er16
Er7
Er11
Er16
Er2
Er1
Er14
Er1
Er3
Ru2
Te1
Er4
Er7
Er4
Er12
Er13
Er14
Er15
Er16
Er17
Ru4
Ru5
Tu3
Er15
Er14
Er9
Er3
Er5
Er17
Er5
Ru2
Er4
Er6
Er3
Er3
Er17
Ru2
Te1
Ru3
Er6
Er18
Er13
Ru5
Te2
Er14
Er6
Er4
Er7
Er4
Er14
Er10
Ru3
Er6
Er11
Er13
Er18
Er8
Er3
Er17
Er7
Ru4
Ru5
Ru6
Er5
Ru6
Ru2
Te1
Er17
Er16
Er3
Er15
Er12
Ru3
Ru5
Te3
Er12
Er15
Er9
Er13
Er15
Er14
Er12
Er10
Er5
Er6
Er8
Er1
Er13
Er12
Er11
Er7
Er6
Er7
Er8
Ru3
Te2
Ru2
Er4
Er16
Er8
Ru5
Ru4
Te2
Er1
Er14
Er17
Er7
Er17
Er18
Er4
Er12
Er8
Te1
Te2
Te3
Er13
Ru3
Te1
Ru1
Er2
Er10
Er13
Er18
Ru6
Ru1
Te3
Er5
Er2
Er1
Er7
Er3
Er6
Er6
Er11
Er4
Er8
Er1
Er8
Er10
Er15
Er13
Er17
Er14
Er16
Er9
Er14
Ru6
Ru4
Te2
Er16
Er18
Er5
Er5
Er11
Er18
Ru2
Ru6
Te2
Er5
Er6
Er12
Er18
Er11
Er15
Er17
Er4

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875
Fig. 3. Puckered hexagonal channel about Te1 defined by the face-sharing
Ru-TCTP; [0 1 0] view.
Most Er–Er separations in Er17Ru6Te3 appear relatively
˚
Fig. 1. The crystal structure of Er17Ru6Te3: (a) slightly off [0 1 0] section
of one-half of the monoclinic cell. Ru (black) centers the Er-based TCTP
(dark gray), and rectangular-face-shared BCTP (light gray), with Er–Er
(gray) and Er–Ru (black) bonds marked. Bonding to Te (white) within the
TCTP is not shown for clarity. (b) Corrugation in a section of the 2D layer
viewed approximately along [1 0 1]. The partial boundaries of the unit cell
are shown in black.
uniform, over a range of ꢁ3.3–3.6 A. All Er have a single
Te neighbor in an adjoining tunnel except for the unusual
bridging Er9 and Er10 (below). The shortest d(Er–Er) are
˚
for Er4–Er6 and Er6–Er14, ꢁ3.3 A, whereas even longer
d(Er–Er) values occur for Er pairs 7–14, 3–17, and 1–11,
˚
3.66, 3.78, and 3.84 A. It is noteworthy that all of these
shorter and longer separations occur in the seam between
the Te1 and the Te2, Te3 regions at the outside edges of the
darker area in Fig. 1 (and Fig. 4 below) in which much of
the strain must be located.
The Te1 atoms are, as for Ru, surrounded by nine-
membered TCTPs of Er, Fig. 3. These channels are defined
by distorted edge-sharing Ru-centered TCTPs, which mean
that the hexagonal edges seen in projection are puckered,
and the channels exhibit different bonding environments
along [001] and [100]. The TCTP rings about each Te1 are
shared along [001], the dark area in Fig. 1a, with a stacking
angle of b ¼ 95.121.
Fig. 4 illustrates how the remaining Te2 and Te3 in
Er17Ru6Te3 are accommodated within pairs of adjacent
TCTP hexagonal channels that extend along [001]. This
Fig. 2. Main building blocks in Er17Ru6Te3. (a) RuEr9: a TCTP with dark
gray Ru–Er bonds in trigonal prism and white bonds to face-capping
atoms. (b) Ru2Er12: a pair of rectangular-face-sharing bicapped trigonal
prisms (BCTP)2 in which the shared face is marked by thicker white Er–Er
bonds.
1
area is centered around the 2 0 0 planes (x ¼ 0, ) and thus
2
appears split at the two outside edges of the area shown in
Fig. 1a, a separate representation being used to retain
details in the figures. The polyhedra about the two Te
are seen to be interconnected along [100] via tilted pairs
of rectangular-face-sharing (BCTP)2 units (11½Ru2Er12ꢃ)
(Fig. 2b). These (BCTP)2 units are further interconnected
along [0 0 1] by two outer (face capping) Er9, Er10 atoms
which lie on special positions and are inter-related by z ¼ 12.
The different arrangements of two different construction
polyhedra, viz., TCTP and (BCTP)2, give rise to three
˚
The prism heights are all the same, b ¼ 4.00 A, and the
structure adapts to the somewhat larger Te by lengthening
˚
the basal edges and thereby d(Te–Erprism) by about 0.4 A to
˚
yield a range of 3.2 to 3.4 A (Table 3). This in effect
˚
decreases the face capping d(Te–Erf.c.) to around 3.1 A. The
bonding of Ru within the TCTP of Er involves very
different types of interactions than for Te within Er TCTP.

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876
Fig. 4. Pairs of trigonal prismatic Er channels that define Te2 and Te3 sites. The framework is made up of rectangular-face-shared BCTP (light-gray
1
polyhedra) along [0 1 0] and corner-shared Er9 and Er10 along [0 0 1]. The Te2, Te3, and Er9, Er10 pairs are each related by zꢁ2 (see text).
distorted hexagonal channel types for the anions, Te1 in
Fig. 3, and paired channels between (BCTP)2 for Te2 and
Te3 (Fig. 4). Nearly a regular difference, 0, 0, ꢁ2, can be
phases are second and third in terms of fractional metal
contents.
1
found between Te2 versus Te3 coordinates (Table 2) on
consideration of equivalent positions, but this is only an
isolated pseudo-symmetry in space group C2/m. The roles
of the formal Teꢀ2 in all of this family of compounds are
principally those of large spacers between or within
polymetal cationic clusters, in contrast to the much more
structurally specific roles the anions play in metal-rich
halides of the same elements [11].
4. Conclusions
The highly condensed, metal-rich ternary telluride
Er17Ru6Te3 has been synthesized by high-temperature
annealing after arc-melting. The complex crystal structure
of Er17Ru6Te3 can be visualized in terms of condensed
Ru-centered TCTP and face-sharing (BCTP)2 of Er in an
array that also generates three types of parallel channels of
TCTP of Er that bind Te. The metal-richest portions of
ternary rare-earth metal–transition-metal–tellurium sys-
tems have evidently not been well investigated, and more-
detailed explorations will definitely uncover more novel
compounds.
The occurrence of both TCTP and rectangular-face-
sharing (BCTP)2 polyhedra appears to be unique to this
structure. Some rare-earth metal–transition-metal tellur-
ides are fully constituted of only TCTP rare-earth metals,
for example, R6ZTe2 (R ¼ Sc; Z ¼ Ru, Rh, Ir, Os [13];
R ¼ Sc; Z ¼ Mn, Fe, Co, Ni, Cu, Ag, Cd [14,15]; R7Z2Te2
(R=Er; Z=Ni, Ir [22,35]; R=Lu; Z=Ni, Pd, Ru [23];
R ¼ Y, Z ¼ Os, Pt [35].) We are not aware of any other
example containing (BCTP)2. The compound Er17Ru6Te3
is the fourth in a series of the rare-earth metal richest
tellurides after Lu8Te, Lu7Te [28], and the newly discovered
and even more condensed. Er21Ir8Te4 [36], but the ternary
Acknowledgment
This research was supported by the National Science
Foundation, Solid State Chemistry, via Grant DMR-
0444657 and was performed in the US Department of
Energy’s Ames Laboratory at Iowa State University.

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877
Appendix A. Supplementary data
[13] L. Chen, J.D. Corbett, Inorg. Chem. 43 (2004) 436.
[14] P.A. Maggard, J.D. Corbett, Inorg. Chem. 39 (2000) 4143.
[15] L. Chen, J.D. Corbett, Inorg. Chem. 41 (2002) 2146.
The CIF file can be obtained from the Fachinforma-
tionszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen,
Germany (fax: +49 7247 808 666; e-mail address: crysda-
ta@fiz.karlsruhe.de) on quoting the depository number
CSD-391431. A [010] projection of the complete unit cell of
Er17Ru6Te3 with the atoms labeled is available on the Web
version of this publication.
[16] P.A. Maggard, J.D. Corbett, J. Am. Chem. Soc. 122 (2000) 10740.
[17] L.M. Castro-Castro, L. Chen, J.D. Corbett, J. Solid State Chem. 180
(2007) 3172.
[18] P.A. Maggard, J.D. Corbett, Angew. Chem. Int. Ed. Engl. 18 (1997)
11974.
[19] P.S. Herle, J.D. Corbett, Inorg. Chem. 40 (2001) 1858.
[20] B.G. Hyde, S. Andersson, Augmented trigonal prismatic construc-
tions, Inorganic Crystal Structures, Wiley-Interscience Publishers,
New York, 1989, p. 80.
Supplementary data associated with this article can be
found in the online version at doi:10.1016/j.jssc.2007.11.020.
[21] F. Meng, C. Magliocchi, T. Hughbanks, J. Alloys Compd. 358 (2003)
98.
[22] F. Meng, T. Hughbanks, Inorg. Chem. 40 (2001) 2482.
[23] L. Chen, J.D. Corbett, Inorg. Chem. 43 (2004) 3371.
[24] P.A. Maggard, J.D. Corbett, Inorg. Chem. 38 (1999) 1945.
[25] P.A. Maggard, J.D. Corbett, Inorg. Chem. 43 (2004) 2556.
[26] C. Magliocchi, F. Meng, T. Hughbanks, J. Solid State Chem. 177
(2004) 3896.
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