K1.10Zr2Se6, Rb0.86Zr2Se6 and Cs0.80Zr2Se6. The first intercalation compounds of zirconium triselenide

Article abstract of DOI:10.1515/znb-2002-1111

Single crystals of K_1.10Zr₂Se₆, Rb_0.86Zr₂Se₆ and Cs_0.80Zr₂Se₆ were obtained by reacting powdered mixtures of A₂Se (A = K, Rb, Cs), Zr and Se at 850°C. K_1.10Zr₂Se₆ and Rb_0.86Zr₂Se₆ crystallize in space group Immm (Z = 2), with a = 3.746(3), b = 5.354(8), c = 21.929(3) A and a = 3.756(1), b = 5.354(8), c = 22.81(1) A?, respectively. Cs_0.80Zr₂Se₆ crystallizes in space group Cmc2₁ (Z = 2), with a = 3.747(1), b = 24.102(5), c = 5.332(2) A?. The compounds are characterized by complex anionic layers ∞²[Zr₂Se₆]_x- with intercalated alkali cations. As in ZrSe₃, the layers are built from columns of trigonal prisms ∞¹[ZrSe₃], connected by additional waist contacts, yielding an eightfold coordination for the Zr atoms. The mean Zr-Se bond lengths correspond to those found in the binary compound. The Se-Se bond lengths are significantly altered, however, indicating a reduction of the Se-Se bond order due to the electron transfer from the alkali metal.

Full text of DOI:10.1515/znb-2002-1111

K1.10Zr Se , Rb Zr Se and Cs Zr Se .
2
6
0.86
2
6
0.80
2
6
The First Intercalation Compounds of Zirconium Triselenide
Kurt O. Klepp, Norbert A. Harringer, and Andreas Kolb
Abteilung f u¨ r Allgemeine und Anorganische Chemie Universit a¨ t Linz,
Altenbergerstr. 69, A-4040 Linz
Reprint requests to Prof. Dr. K. O. Klepp. Fax: +43-7322-4688800. E-mail: kurt.klepp@jku.at
Z. Naturforsch. 57 b, 1265–1269 (2002); received September 10, 2001
Complex Chalcogenides, Selenides, Zirconium
Single crystals of K1 10Zr
powdered mixtures of A Se (A = K, Rb, Cs), Zr and Se at 850 C. K1 10Zr
crystallize in space group Immm (Z = 2), with a = 3.746(3), b = 5.354(8), c = 21.929(3) A
2
Se
6
, Rb0 86Zr
2
Se
6
and Cs0 80Zr
2
Se
6
were obtained by reacting
2
2
Se and Rb0 86Zr Se
6
2
6
˚
˚
2 6
and a = 3.756(1), b = 5.354(8), c = 22.81(1) A, respectively. Cs0 80Zr Se crystallizes in space
˚
1
(Z = 2), with a = 3.747(1), b = 24.102(5), c = 5.332(2) A. The compounds are
x
group Cmc2
characterized by complex anionic layers [Zr
3
ZrSe , the layers are built from columns of trigonal prisms [ZrSe ], connected by additional
2
2
Se
6
]
with intercalated alkali cations. As in
1
3
waist contacts, yielding an eightfold coordination for the Zr atoms. The mean Zr-Se bond lengths
correspond to those found in the binary compound. The Se-Se bond lengths are significantly
altered, however, indicating a reduction of the Se-Se bond order due to the electron transfer
from the alkali metal.
Introduction
finally heated in a vacuum to 200 C in order to remove
the excess of the alkali metals.
In an argon glove box the A
mixed with Zr powder (300 mesh, Alfa Ventron) and
Recent investigations in the chalcogen rich sec-
tions of the ternary systems A/T /Q (A = alkali
metal, T = Ti, Zr, Hf, Q = Se, Te) have revealed nu- grey Se powder in the molar ratio 1:4:11 (75.5 mg K Se,
2
Se educts were intimately
IV
2
merous new ternary polychalcogenides [1 - 5]. As 176.1 mg Zr, 425.9 mg Se; 252.9 mg Rb
a common structural feature they are built from in- Zr, 880.6 mg Se and 284.7 mg Cs Se, 306.5 mg Zr,
2
Se, 369.3 mg
2
1
p
finite polyanionic chains, [T Q ] , with differ- 717.7 mg Se, resp.), transferred to silica ampoules which
m
n
2
were sealed in a vacuum of 10 Pa.
ent chalcogen contents. Typically these compounds
are located at cation rich compositions beyond the
equiatomic A:T ratio or along the equiatomic A:T
line.
Diminishing the relative content of the alkali
metal should favour the formation of polyanions
of higher dimensionality towards layered or frame-
work partial structures. The search for new layered
The samples were gradually heated to 850 C, held
at this temperature for 3d and finally allowed to attain
ambient temperature at a constant cooling rate of 2 C/h.
The reaction products consisted of needle shaped crys-
tals which showed metallic luster and were extremely
delicate to handle because of their fragility. They had to
be handled under inert conditions. Attempts to synthe-
size homologous selenohafnates by this high temperature
compounds was the stimulus for our present inves- method were unsuccessful.
tigation in the transition metal rich section of the
Preliminary X-ray investigations by Weissenberg
IV
ternary A/T /Q systems. As a first result the new methods revealed an orthorhombic body-centered unit-
cell for the potassium- and the rubidium phase and an or-
ternary compounds A Zr Se of the heavier alkali
x
2
6
thorhombic C-centered unit-cell for the cesium phase. For
the determination of the crystal structures, fragments with
metals are presented below.
3
the approximate dimensions 0.175 0.025 0.007 mm
Experimental Section
3
for the potassium phase, 0.125 0.025 0.025 mm for
2
The starting materials A Se (A = K, Rb, Cs) were syn- the rubidium phase and 0.175 0.175 0.025 for the
thesized at –40 C by reacting alkali metals (99.9%, Alfa cesium phase were selected, embedded in a thin walled
Ventron, 5% excess) with Se powder (99.999%, Asarco) glass capillary and transferred to a Kappa diffractome-
in liquid ammonia. The reaction products were dried and ter (Enraf Nonius Turbo CAD 4) operated with graphite
0
932–0776/02/1100–1265 $ 06.00 c 2002 Verlag der Zeitschrift f u¨ r Naturforschung, T u¨ bingen www.znaturforsch.com
K
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1
266
K. O. Klepp et al. · Intercalation Compounds of Zirconium Triselenide
Table 1. Crystallographic data of K1 10Zr
2
Se
6
, Rb0 86Zr
2
Se
6
and Cs0 80Zr
2
Se
6
K
1 10Zr
2
Se
6
Rb0 86Zr
oI18
3.756(1)
5.359(4)
22.81(1)
2
Se
6
Cs0 80Zr
oC18
2 6
Se
Pearson symbol
oI18
˚
a [A]
3.746(3)
5.354(8)
21.929(3)
3.747(1)
˚
b [A]
24.102(5)
5.332(2)
˚
c [A]
Space group
Immm (No.71)
2
Immm (No.71)
2
Cmc2
2
481.5
5.26
762.53
277.48
1
(No. 36)
Z
3
˚
V [A ]
439.8
459.1
3
d
x
[g cm
]
5.28
699.21
276.33
5.26
729.70
303.52
M
r
(
1
Mo-K ) [cm ]
Structure refinement:
Unique reflections
Observed reflections
Cutoff
414
356
438
268
292
336
2
2
2
3.00 [F
22
0.052
0.047
2.96
o
]
3.00 [F
22
0.035
0.034
1.72
o
]
3.00 [F
32
0.045
0.051
2.95
o
]
Variables
R = Σ |F
o
| – |F
[Σ w |F | – |F
Residual electron density [eA
c
| / Σ |F
o
|
2
2 1
2
=
o
c
|
/ Σ w|F
o
| ]
3
˚
]
2
2
2 2 1 2
w = [ [F
o
] + [0.005 F
o
] ]
.
Table 2. Positional parameters and temperature factors of K1 10Zr
2
Se
6
, Rb0 86Zr
2 6 2 6
Se and Cs0 80Zr Se WP = Wyckoff
2
i i ij i j i j
position; PP = Population parameter; Beq = (8 /3)Σ Σ U a a a a , where U12 = U13 = 0 by site and space group
symmetry .
Atom WP
Se
x
y
z
PP
U
11
U
22
U
33
U
23
B
eq
K
1.10Zr
2
6
:
K(1)
K(2)
Zr(1)
Se(1)
Se(2)
2a
2b
4j
0
0
1/2
0
0
0
1/2
0
0
0.64 0.04(1)
0.46 0.03(1)
0.13(2)
0.12(3)
0.005(1)
0.003(1)
0.010(8)
0.06(2)
0.008(1)
0.008(1)
0
0
0
0
4.6(6)
5.(1)
0.50(5)
0.50(5)
1.00(3)
0
0.3186(1)
0.2287(1)
1
1
1
0.006(1)
0.008(1)
4i
0
8l
–0.2431(5) 0.38953(9)
0.0117(7) 0.0153(9) 0.0110(7) 0.002(1)
Rb0.86Zr
Rb(1) 2a
Rb(2) 2b
Zr(1)
Se(1)
Se(2)
2
Se
6
:
:
0
0
1/2
0
0
0
1/2
0
0
0.5 0.042(4)
0.36 0.034(5)
0.048(4)
0.041(5)
0.016(3)
0.007(4)
0
0
0
0
2.7(1)
0
2.9(2)
4j
4i
8l
0.31616(8)
0.22963(8)
1
1
1
0.0050(7) 0.0042(6) 0.0063(8)
0.0052(7) 0.0028(6) 0.0051(8)
0.0093(5) 0.0105(5) 0.0107(6) 0.0011(5) 0.81(2)
0.42(3)
0.37(3)
0
–0.2429(3) 0.38414(6)
2 6
Cs0.80Zr Se
Cs(1)
Zr(1)
Se(1)
Se(2)
Se(3)
4a 1/2 0.5017(3)
4a 1/2 0.31249(9)
4a 1/2 0.23045(9)
4a 1/2 0.1225(2)
0.228(2)
0.208(2)
0.199
0.4592(6)
0.441(6)
0.40 0.040(2)
0.028(2)
0.040(3)
0
0
0
0
2.8(1)
1
1
1
1
0.0034(7) 0.0162(9) 0.0047(7)
0.0041(7) 0.0142(9) 0.0043(7)
0.64(3)
0.59(3)
1.22(5)
0.0009(9) 0.034(1)
0.011(1)
4a
0
0.3775(1)
0.010(1) 0.0075(9) 0.015(1)
0.0011(5) 0.86(4)
monochromated MoK -radiation. Intensity data collec- sitions of 25 high angle reflections. Their values and other
tions were performed at ambient temperatures over an crystallographic data are summarized in Table 1.
octant of the reflection sphere. Crystal and orientation sta-
The crystal structures were solved by direct methods
bility were monitored using three periodically determined (Multan 82) [6] in the centrosymmetric space groups
control reflections. Finally precise lattice constants were Immm for the potassium- and the rubidium phase and
obtained by least squares’ refinements of the angular po- in Cmc2 for the cesium phase which yielded the anionic
1
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K. O. Klepp et al. · Intercalation Compounds of Zirconium Triselenide
1267
Fig. 1. Projection of the crystal structures of ZrSe
3
, Rb0 86Zr
2
Se
6
and Cs0 80Zr
2
Se
6
along the shortest crystallographic
axis. Zr-Se bonds are indicated by open, Se-Se bonds by hatched rods, resp.
network. The positions of the alkali metal atoms were running parallel to (001) (K and Rb compound) and
obtained from difference Fourier syntheses. Full matrix (010) (Cs compound), respectively. These layers are
least squares’ refinements rapidly converged to R values
of 0.052, R = 0.047 (K compound), R = 0.035, R
.034 (Rb compound), R = 0.045 and R = 0.051 (Cs
compound). Subsequent difference Fourier maps were
featureless. A refinement of the Flack parameter con-
separated from each other by planar sheets of al-
kali cations. While the K- and Rb- compounds are
isotypic (space group Immm with Z = 2), the ce-
sium compound adopts a different structure type
w
w
=
0
w
(
space group Cmc2 with Z = 2). Nevertheless the
1
2 6
firmed the enantiomorph chosen for Cs0 80Zr Se .
complex anions in both structure types are closely
related with each other. They are built up by trigo-
All calculations were performed with programs of
the MolEN [7] crystallographic software package using
conventional scattering factors for neutral atoms. The
data were corrected for absorption using an empirical
method [8]. The final positions and anisotropic tempera-
ture factors are given in Table 2.
nal ZrSe -prisms sharing their basal faces to form
6
columns which in turn are connected through addi-
tional Zr-Se waist contacts yielding double layers.
The atomic arrangement within the layered anions
are intimately related to that of the binary compound
Further details on the structure refinements have
been deposited with the Fachinformationszentrum Karls-
ZrSe [9] (= ZrSe(Se) ) which adopts the TiS [10]
3
2
3
˚
˚
structure type, P2 /n with a = 5.410 A, b = 3.770 A,
c = 9.450 A, = 97.5 , Z = 2. A synoptic view of
ruhe under CSD. Nos. 412723 (K1 10Zr
2
Se
6
) 412724
1
˚
(
Rb0 86Zr
2
Se ) 412732 (Cs0 80Zr Se ), respectively
6
2
6
the three structure types is given in Fig. 1 in pro-
jection along the prism axes. In contrast to ZrSe3,
neighbouring layers in the ternary chalcogenides are
Results and Discussion
The new ternary chalcogenides K1 10Zr Se , alternatingly shifted by half the prism height which
2
6
Rb0 86Zr Se and Cs0 80Zr Se crystallize with leads to a doubling of the stacking sequence and al-
2
6
2
6
novel structure types which are characterized by in- lows the formation of interstices of appropriate size
hosting the alkali cations.
finite complex anionic double layers, 2 [Zr Se ] ,
x
2
6
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1
268
K. O. Klepp et al. · Intercalation Compounds of Zirconium Triselenide
˚
Table 3. Synoptic table of selected interatomic distances [A] of ZrSe
3
, K1 10Zr
2
Se
6
, Rb0 86Zr
2
Se
6
and Cs0 80Zr
Se
2 6
Se .
ZrSe
3
[9]
K
1 10Zr
2
Se
6
Rb0 86Zr
2
Se
6
Cs0 80Zr
2
6
Coordination of the alkali cations
K(2)-Se(2) 3.327(1) 8
K(1)-Se(2) 3.357(1) 8
Rb(2)-Se(2) 3.493(1) 8
Rb(1)-Se(2) 3.523(1) 8
Cs(1)-Se(2) 3.68(1)
Cs(1)-Se(3) 3.71(1)
Cs(1)-Se(3) 3.78(1)
Cs(1)-Se(2) 3.81(1)
2
2
2
2
Zr-Se Bond distances*
Zr(1)-Se(1) 2.72 2x Zr(1)-Se(1) 2.719(2) 4x Zr(1)-Se(1) 2.725(2) 4x Zr(1)-Se(1) 2.724(2) 2x
Zr(1)-Se(2) 2.74 2x Zr(1)-Se(2) 2.761(1) 2x Zr(1)-Se(2) 2.761(1) 2x Zr(1)-Se(3) 2.743(6) 2x
Zr(1)-Se(3) 2.75 2x Zr(1)-Se(3) 2.871(1) 2x Zr(1)-Se(3) 2.876(1) 2x Zr(1)-Se(2) 2.779(8) 2x
Zr(1)-Se(1) 2.87
Zr(1)-Se(1) 2.87
Mean value: 2.771
Zr(1)-Se(1) 2.81(1)
Zr(1)-Se(1) 2.90(1)
2.776
2.763
2.771
Shortest Se-Se distances*
Se(2)-Se(3) 2.34
Se(2)-Se(3) 3.06
Se(2)-Se(2) 2.603(2)
Se(2)-Se(2) 2.751(2)
Se(2)-Se(2) 2.602(3)
Se(2)-Se(2) 2.757(3)
Se(2)-Se(3) 2.572(4)
Se(2)-Se(3) 2.760(4)
*
No estimated standard deviations are given in Ref. [9].
2 6 2 6
Fig. 2. The different coordination of the alkali cations in the crystal structures of Rb0 86Zr Se and Cs0 80Zr Se . The
alkali positions are only partially occupied, the occupation of the smaller Rb(2) site is significantly lower than that of
the Rb(1) site.
The alkali cations adopt eightfold chalcogen co- of this position. This site is apparently too small for
+
ordinations in prismatic or almost prismatic con- the Cs ions, which may be the main reason for the
figurations, shown in greater detail in Fig. 2. In formation of a different structure in Cs0 80Zr Se6
2
K1 10Zr Se and Rb Zr Se the cations occupy where the Cs atoms occupy only one crystallo-
2
6
0 86
2
6
two crystallographically different split positions 2a graphic site (4a).
A(1) and 2b A(2), respectively. The coordination
prism around 2b has shorter edges along [010] (four
diselenide groups with a bond length of 2.60 A).
Individual bond lengths within the anionic layers
are summarized in Table 3 and compared to those
˚
of ZrSe . The zirconium atoms are in bicapped
3
This is reflected by a significantly lower occupancy
trigonal prismatic chalcogen coordinations. Zr-Se
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K. O. Klepp et al. · Intercalation Compounds of Zirconium Triselenide
1269
˚
bonds within the trigonal prisms are in the range of with d = 2.34 A yields bond orders of n = 0.47
0
˚
.719(2) to 2.779(8) A, while the two Zr-Se bonds (Cs0 80Zr Se ) and n = 0.43 (Rb Zr Se and
2 6 0 86 2 6
provided by the waist contacts are only about 0.1 A K1 10Zr Se ), respectively which is far lower
2
˚
2
6
longer. The average Zr-Se bond lengths range from than the expected value (0.75 for stoichiometric
˚
.763 to 2.776 A, in excellent agreement with those AZr Se ). An inspection of the Se-Se intergroup
2 6
found in ZrSe3.
2
˚
distances of only 2.75 A shows that bonding Se-
Since the insertion of the alkali metal apparently Se-interactions should no longer be neglected, since
does not influence the Zr-Se bond lengths, it can be they correspond to bond orders of about 0.26. This
concluded that the oxidation state of the transition yields “overall” bond orders of 0.73 (Cs compound)
metal atom remains unchanged. This is corrobo- and 0.69 (Rb and K compound). Though these val-
rated by an inspection of the Se-Se distances. In the ues are still too low for the substoichiometric Cs and
binary compound a discrete diselenide group with a Rb compounds, they reflect the trend correctly, i. e.
˚
homonuclear bond of 2.34 A is found. The shortest the higher bond order is associated with the lower
˚
distance between the diselenide groups is 3.06(7) A, alkali metal content.
which indicates only weak Se-Se-interactions.
From the bonding considerations above and the
In the title compounds, however, the bond dis- close structural relationships it becomes evident,
tances within the diselenide groups are widened sig- that the title compounds should be seen as in-
˚
˚
nificantly to 2.572(4) A (Cs Zr Se ) and 2.603 A tercalation compounds of ZrSe . It should there-
0
80
2
6
3
(
K1 10Zr Se and Rb Zr Se ), respectively.
fore be interesting to study the reversibility of the
2
6
0 86
2
6
This might be taken as an indication that an elec- intercalation process by electrochemical methods.
tron transfer has occurred from the alkali metal to The elevated displacement parameters U of the K
22
the diselenide group causing a decrease of the Se-Se cations in K1 10Zr Se in particular may indicate
2
6
bond order. Application of Pauling’s bond order / enhanced ionic mobility, making this compound
bond length relationship [11]
a promising candidate for corresponding electro-
chemical experiments. Investigations in this field
are currently in preparation.
d = d – 0.71 log n
0
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(
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6] P. Main, S. J. Fiske, S. Hull, L. Lessinger, G. Ger-
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1
1/82, A System of Computer Programs for the [10] S. Furuseth, Acta Chem. Scand. A29, 623 (1975).
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