Synthesis, crystal structure and properties of Ag4CuTeO 6

Article abstract of DOI:10.1002/zaac.200600292

The new quaternary oxide Ag₄CuTeO₆ has been obtained by solid state reaction starting from stoichiometric amounts of the binary oxides at elevated temperatures and oxygen pressures. Ag₄CuTeO ₆ crystallises in space group C2/c with a = 11.3021(8), b = 9.6875(6), c = 5.7082(5) A, β = 99.301(7)°, V = 616.77(8) A³, Z = 4; the structure refinement was based on 747 independent reflections and resulted in R₁ = 3.26 %, wR₂ = 7.29 %. The crystal structure consists of isolated TeO₆ octahedra which are connected by distorted CuO₄ squares, thus forming one-dimensional, infinite heteropolyanions, extending along the c axis. According to the approximately fcc packing and a distorted octahedral oxygen environment of all the cations, the structure may be regarded a derivative of the NaCl structure type. Ag₄CuTeO₆ is paramagnetic between 300 K and 7 K, where it develops antiferromagnetic ordering. An evaluation according to the Curie-Weiss law yielded a magnetic moment of 1.86 μ_B per copper ion. The electronic conductivity shows a maximum at ～ 75 K, below a temperature characteristic of a semiconductor, above of a metal.

Full text of DOI:10.1002/zaac.200600292

DOI: 10.1002/zaac.200600292
Synthesis, Crystal Structure and Properties of Ag CuTeO
4
6
Wilhelm Klein, Jan Curda, and Martin Jansen*
Stuttgart, Max-Planck-Institut für Festkörperforschung
Received September 10th, 2006.
Abstract. The new quaternary oxide Ag
by solid state reaction starting from stoichiometric amounts of the
binary oxides at elevated temperatures and oxygen pressures.
4
CuTeO
6
has been obtained
ment of all the cations, the structure may be regarded a derivative
of the NaCl structure type.
Ag
lops antiferromagnetic ordering. An evaluation according to the
Curie-Weiss law yielded a magnetic moment of 1.86 µ per copper
4 6
CuTeO is paramagnetic between 300 K and 7 K, where it deve-
4 6
Ag CuTeO crystallises in space group C2/c with a ϭ 11.3021(8),
˚
˚
3
b ϭ 9.6875(6), c ϭ 5.7082(5) A, β ϭ 99.301(7)°, V ϭ 616.77(8) A ,
Z ϭ 4; the structure refinement was based on 747 independent
B
ion. The electronic conductivity shows a maximum at ϳ 75 K,
below a temperature characteristic of a semiconductor, above of
a metal.
reflections and resulted in R
structure consists of isolated TeO
by distorted CuO squares, thus forming one-dimensional, infinite
1
ϭ 3.26 %, wR
2
ϭ 7.29 %. The crystal
6
octahedra which are connected
4
heteropolyanions, extending along the c axis. According to the ap-
proximately fcc packing and a distorted octahedral oxygen environ-
Keywords: Tellurium; Copper; Silver; High oxygen pressure synthesis;
Magnetism
Introduction
which were also found in Ag Hg (TeO ) [14], Ag Te O
6
2
2
4 3
2
2
[15], occurring in two polymorphic modifications, forms
Oxides of metals with unpaired electrons adopting crystal
structures with low-dimensional building units often exhibit
intriguing physical properties, in particular with respect to
magnetism and electronic conductivity [1Ϫ3]. Such low-di-
mensional structures can cause highly anisotropic physical
properties since interactions between electrons, e.g. mag-
netic coupling, preferably develop following the crystallo-
graphic orientation of the substructures. Ternary silver(I)
oxides quite commonly exhibit such kind of crystal struc-
tures with anionic partial structures which are highly aniso-
tropic [4Ϫ11]. This is caused by the characteristic tendency
of monovalent silver to form extended aggregates of Ag
atoms resembling sections of the element’s structure, and
therefore to induce a clear separation of cationic and
anionic parts of the crystal structure. From ternary silver
oxides anionic structures in dimensionalities from zero to
three are known, thus including chains, layers and three-
dimensional networks. We have started investigating ternary
silver tellurates, and have noticed that this family of com-
pounds shows an impressive chemical and crystal chemical
variety, depending on the content of silver: Ag TeO [12]
layers, while three-dimensional networks are found in Ag2-
Te O [15] and in the pyrochlore-related Ag Te O [16].
4
11
2
2
7
However, all these tellurates do not contain unpaired elec-
trons and thus are diamagnetic and electrochemically
insulating. We have started to use these compounds as
matrices for introducing additional electronically active
transition metals with the intention to produce materials
with interesting properties.
Here we report on a first result obtained at inserting cop-
per into silver tellurates, the synthesis, crystal structure and
properties of Ag CuTeO .
4
6
Experimental Section
Ag CuTeO was prepared by reacting of Ag O (freshly pre-
4
6
2
cipitated), TeO (Fluka, p. a.) and CuO (Merck p.a.) in
2
stainless steel autoclaves at elevated oxygen pressures [17].
Stoichiometric amounts of these oxides were intimately
mixed and placed into gold tubes which were sealed from
one side and mechanically closed (not gas-tight) from the
other. Black, polycrystalline samples of Ag CuTeO were
6
6
contains isolated TeO octahedra, Ag TeO [13] consists of
6
2
4
chains which represent sections of the rutile structure,
4
6
obtained under an oxygen pressure of 380 to 420 MPa
within the temperature range of 400 to 550 °C. In a typical
*
Prof. Dr. Martin Jansen
experiment, Ag CuTeO was synthesized from a mixture of
4 6
Max-Planck-Institut für Festkörperforschung
Heisenbergstraße 1
D-70569 Stuttgart/Germany
Tel.: ϩ49 711 689 1500
232 mg Ag O (2 mmol), 40 mg CuO (0.5 mmol) and 80 mg
2
TeO (0.5 mmol) reacted at 415 MPa oxygen pressure and
2
5
00 °C for 2 d. To prepare single crystals suitable for
X-ray diffraction analysis, 1 ml H O was added to the start-
Fax: ϩ49 711 689 1502
2
E-Mail: m.jansen@fkf.mpg.de
ing mixture as mineraliser.
Z. Anorg. Allg. Chem. 2007, 633, 231Ϫ234
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
231

W. Klein, J. Curda, M. Jansen
X-ray diffraction powder data were collected with a Stoe Stadi-P
diffractometer (Cu KͰ , Ge monochromator, linear PSD) in steps
b
˚
2
4 6
Table 4 Anisotropic displacement parameters in A for Ag CuTeO .
1
of 0.1° over a 2θ range from 10 to 90° for 24 h. The observed
Atom
U
11
U
22
U
33
U
23
U
13
U
12
reflections are listed in Table 1.
Ag(1)
Ag(2)
Ag(3)
Cu
0.0444(8)
0.0230(7)
0.0193(4)
0.0166(9)
0.0123(5)
0.017(3)
0.017(3)
0.015(3)
0.0130(5)
0.0436(9)
0.0337(6)
0.0110(8)
0.0112(4)
0.017(3)
0.013(3)
0.019(3)
0.0190(5)
0.0325(7) Ϫ0.0027(5)
0.0261(4) Ϫ0.0046(3)
0.0130(7)
0.0067(4)
0.017(3) Ϫ0.002(3)
0.016(3) Ϫ0.005(2)
0.012(3) Ϫ0.002(3)
0
0.0044(5)
0.0160(6)
Ϫ0.0045(4)
0.0042(7)
0.0011(3)
0.002(3)
0
0.0004(5)
Ϫ0.0002(3)
0
Table 1 Experimental X-ray powder data for Ag
4
CuTeO
6
with
0
0
˚
Te
0
d > 1.48 A.
O(1)
O(2)
O(3)
Ϫ0.013(3)
0.001(3)
Ϫ0.007(3)
0.001(3)
0.000(3)
˚
˚
˚
d
obs [A] I / I
0
h
k
l
d
obs [A] I / I
0
h
k
l
d
obs [A] I / I
0
h
k
l
b
ij are defined as exp[Ϫ2π (U11h a ϩ U22k b ϩ U33l c ϩ U12hka*b* ϩ U13hla c*
2
2
*2
2
*2
2
*2
*
7
4
4
3
3
3
2
2
2
2
2
2
2
.3112
.7095
.2484
.6721
.1765
.1028
.9328
.7885
.6946
.6672
.5330
.4378
.3701
1.4
5.9 Ϫ1
5.6
8.0
0.8 Ϫ3
1.9
3.4
43.2
54.0 Ϫ2
1
1
1
1
2
1
3
2
0
0
3
1
3
1
0
1
1
1
1
0
1
0
2
1
2
0
2
2.3645 55.1
2
0
2
3
4
1
3
4
3
3
5
1
1
2
2
1
1
0
0
1
1
2
2
0
2
3
3
1.7184
1.6832
1.6807
1.6390
1.6148
1.6030
1.5918
1.5811
1.5602
1.5522
1.5179
1.5127
1.4833
0.8
6.1 Ϫ6
29.4
29.6 Ϫ1
3
5
0
3
3
6
2
2
1
5
6
5
6
4
0
2
1
3
0
3
1
1
2
1
2
1
3
U
*
*
2.3409
2.3287
2.2234
2.1733
2.1558
2.1139
2.0401
1.9483
1.9090
1.8661
1.7742
1.7470
7.6 Ϫ4
95.0 Ϫ3
0.6
1.5
0.8
2.0 Ϫ2
1.2
1.5 Ϫ3
2.7
3.2 Ϫ5
1.0
3.7 Ϫ2
ϩ U23klb c )].
1
0
5
2
5
3
˚
4 6
Table 5 Selected bond lengths /A and angles for Ag CuTeO .
11.3
0.7
0.7
0
2
6
1
2
4
Atoms
Distance
Atoms
Angle
1
1.1 Ϫ7
1.4
2.0
1
0
i
i
i
100.0
1.7
1.6
1
1
3
1
TeϪO(1)
TeϪO(2)
TeϪO(3)
CuϪO(3)
CuϪO(2)
CuϪO(2)
Ag(1) ϪO(3) 2.425(7) [2x]
Ag(1) ϪO(1) 2.479(7) [2x]
Ag(1) ϪO(1) 2.647(6) [2x]
Ag(2)ϪO(1)
Ag(2)ϪO(2)
Ag(2)ϪO(3)
Ag(3) ϪO(2)
Ag(3) ϪO(1)
Ag(3) ϪO(3)
Ag(3) ϪO(3)
Ag(3) ϪO(2)
Ag(3) ϪO(1)
CuϪCu
1.932(6) [2x]
1.948(6) [2x]
1.955(6) [2x]
1.978(6) [2x]
2.002(6) [2x]
2.489(6) [2x]
O(1)ϪTeϪO(2)
O(3)ϪTeϪO(3)
O(1)ϪTeϪO(1)
O(1)ϪTeϪO(2)
O(1)ϪTeϪO(3)
O(1)ϪTeϪO(3)
O(2)ϪTeϪO(2)
O(2)ϪTeϪO(3)
O(2)ϪTeϪO(3)
174.7(3)° [2x]
179.6(4)°
2.0 Ϫ3
1.0 Ϫ2
1
93.0(4)°
8.4 Ϫ3
0.6
0
ii
91.8(3)° [2x]
89.3(3)° [2x]
91.0(3)° [2x]
83.5(4)°
88.2(3)° [2x]
91.4(3)° [2x]
164.0(3)° [2x]
92.1(4)°
95.5(3)° [2x]
80.8(4)°
iii
i
i
i
vi
ii
vi
vi
Table 2 Crystallographic data and details of the structure deter-
mination of Ag
vi
v
4 6
CuTeO .
ii
2.265(6) [2x]
2.679(6) [2x]
2.831(7) [2x]
2.300(7)
2.303(6)
2.634(7)
2.650(6)
2.742(6)
2.769(6)
3.2708(16)
O(2)ϪCuϪO(3)
ii iv
O(3) ϪCuϪO(3)
iv
compound
Ag
4
CuTeO
6
x
i
O(2)ϪCuϪO(3)
O(2)ϪCuϪO(2)
i
i
space group
a
b
c
C2/c (No. 15)
11.3021(8) A
9.6875(6) A
5.7082(5) A
99.301(7)°
616.77(8) A
i
ix
i
vi
vi
ii
O(1) ϪAg(1) ϪO(3) 165.3(2)° [2x]
ii vi iv
˚
i
O(3) ϪAg(1) ϪO(3)
71.9(3)°
ii
˚
i
ix
iii
ix
vii
vi
O(1) ϪAg(1) ϪO(3) 111.6(2)° [2x]
vi vi vii
˚
i
O(1) ϪAg(1) ϪO(1) 68.9(3)°
β
i
O(1)ϪAg(2)ϪO(1)
180°
162.4(2)°
˚
3
cell volume V
formula units Z
molar mass
density (calculated)
absorption coefficient µ
absorption correction
ii
ix
i
i
O(1) ϪAg(3) ϪO(2)
4
718.62 g/mol
7.7391 g/cm
20.478 mm
semi-empirical
5.56Ϫ55.98°
Ϫ14 Յ h Յ 14
Ϫ12 Յ k Յ 12
Ϫ7 Յ l Յ 7
3098
Symmetry codes: (i) Ϫxϩ1, y, Ϫzϩ1/2; (ii) Ϫxϩ1, Ϫyϩ1, Ϫz; (iii) Ϫxϩ1,
Ϫyϩ1, Ϫzϩ1; (iv) x, Ϫyϩ1, zϩ1/2; (v) x, Ϫyϩ1, zϪ1/2; (vi) x, yϩ1, z;
(
3
Ϫ1
vii) Ϫxϩ1, yϩ1, Ϫzϩ1/2; (viii) Ϫxϩ1/2, Ϫyϩ1/2, Ϫzϩ1; (ix) xϩ1/2, Ϫyϩ1/
, zϩ1/2; (x) x, y, zϩ1; (xi) xϩ1/2, yϩ1/2, z.
2
2
θ-range
hkl-region
Single crystal data of Ag
diffractometer with SMART-CCD (APEX) (MoK
monochromator, semi-empirical absorption correction with the
program SADABS [18]).
4
CuTeO
6
were collected on a Bruker AXS
graphite
α
measured reflections
R(int)
independent reflections
4.17 %
747
independent reflections (I 2σ(I))
parameters
545
58
The crystal structure was solved with direct methods [19], all metal
atoms were found at this stage, while the oxygen atoms were local-
ised by Fourier analyses. Further information concerning the data
collection and processing, the crystallographic parameters, as well
as details on structure solution and refinement are given in Table 2.
The atomic coordinates, displacement parameters and bond lengths
and angles are shown in Tables 3-5. Further details of the crystal
structure investigations are available from the Fachinformations-
zentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen, Germany,
on quoting the depository number CSD-416931, the name of the
authors and the citation of the paper.
R(F) (I > 2σ(I) / all data)
3.26 % / 5.32 %
7.29 % / 8.08 %
1.047
2
R
w
(F ) (I > 2σ(I) / all data)
goodness-of-fit (all data)
extinction coefficient
max. difference electron density
min. difference electron density
depository no.
0
Ϫ
˚
Ϫ3
˚
1.76 e A (0.75 A from Ag(3))
Ϫ
˚
Ϫ3
˚
Ϫ1.18 e A (1.30 A from Ag(3))
CSD-416931
Table 3 Atomic coordinates and isotropic displacement parame-
a
˚
2
4 6
ters in A for Ag CuTeO .
Thermal decomposition experiments were performed with a STA
Atom Wyckoff position
x
y
z
U
eq
4
09 (Netzsch, Selb, Germany) with a heating rate of 10 °C/min in
argon atmosphere. The decomposition of Ag CuTeO occurs with
an onset at 600 °C, as solid residues elemental silver, Ag TeO and
Ag(1)
Ag(2)
Ag(3)
Cu
4e
4d
8f
4e
4e
8f
8f
8f
1/2
1/4
Ϫ0.07322(12)
1/4
1/4
1/2
0.02575(15)
1/4
1/4
0.3210(11)
0.3292(11)
Ϫ0.0806(11)
0.0255(3)
0.0318(4)
0.0273(3)
0.0133(4)
0.0101(2)
0.0171(14)
0.0155(14)
0.0155(13)
4
6
2
3
0.23784(7) 0.41857(10)
1/2
1/2
0.3870(5)
0.3987(6)
0.4204(6)
CuO were identified by powder X-ray diffraction. The measured
weight loss at 700 °C was 4.50 % (calc. 4.45 %).
0.58246(17)
0.27509(9)
0.1378(7)
0.4250(6)
0.2759(7)
Te
O(1)
O(2)
O(3)
Magnetic measurements were performed on a SQUID-Magneto-
meter (MPMS 5.5, Quantum Design) between 5 and 350 K in
magnetic fields up to 5 T.
a
2
2
2
U
eq is defined as exp[Ϫ8π U(sin θ/λ )].
232
www.zaac.wiley-vch.de
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2007, 231Ϫ234

4 6
Synthesis, Crystal Structure and Properties of Ag CuTeO
Fig. 1 Coordiations of cations in Ag
4 6
CuTeO , displacement ellip-
soids are drawn at the 50 % probability level, dashed lines represent
˚
˚
distances longer than 2.48 A for Cu-O and 2.62 A for Ag-O separa-
tions. Symmetry codes: (i) Ϫxϩ1, y, Ϫzϩ1/2; (ii) Ϫxϩ1, Ϫyϩ1,
Ϫz; (iii) Ϫxϩ1, Ϫyϩ1, Ϫzϩ1; (iv) x, Ϫyϩ1, zϩ1/2; (v) x, Ϫyϩ1,
zϪ1/2; (vi) x, yϩ1, z; (vii) Ϫxϩ1, yϩ1, Ϫzϩ1/2; (viii) Ϫxϩ1/2,
Ϫyϩ1/2, Ϫzϩ1; (ix) xϩ1/2, Ϫyϩ1/2, zϩ1/2.
1
[CuTeO6]4Ϫ chains in Ag CuTeO , view approximately
4 6
Fig. 2
ϱ
along [Ϫ101]. The chains are connected by Ag(1) cations in direc-
tion of the b axis.
Measurements of the electrical conductivity were performed by the
four-point-probe method (Van-der-Pauw) on pressed pellets (dia-
meter: 6 mm, thickness: 1 mm).
atoms forming 2ϱ [Ag(1)CuTeO6]3Ϫ slabs oriented perpen-
dicular to [100]. These slabs are separated by layers of Ag(2)
and Ag(3) atoms. While Ag(2) and Ag(3) are in an approxi-
mately linear coordination by two oxygen atoms, Ag(1)
atoms are surrounded by a twisted square of oxygen atoms
very similar to the copper case but with considerably longer
M-O separations (Tab.1). These comply well with those of
monovalent silver in a square environment as observed in
the hollandite derivative Ag1.8Mn O [21, 22]. All silver
Results and Discussion
Ag CuTeO has been obtained from solid state reactions of
4
6
its binary components at elevated oxygen pressures. While
the new compound forms rather easily, no further com-
pounds have been found in this quaternary system. When
using starting mixtures of compositions different from the
title compound, always known ternary silver and copper
tellurates were found as by-products. Obtaining copper(II)
at the conditions applied here, is in accordance with our
former findings [20].
8
16
˚
atoms have additional neighbours at distances beyond 2.6 A
resulting in a 4ϩ2 (Ag(1)) and 2ϩ4 (Ag(2), Ag(3)) coordi-
nation, respectively. Thus for all cations a more or less dis-
torted octahedral environment has been found. With re-
spect to the approximately cubic close packing of the cat-
ions in the layered arrangement, the crystal structure of
Ag CuTeO can be regarded as a distorted variant of the
The crystal structure of Ag CuTeO exhibits well known
4
6
4
6
coordination polyhedra for all cations involved. Tellurium
is surrounded by a slightly distorted octahedron of oxygen
α-NaFeO structure type (Fig. 3), or, in an even more gen-
2
eral view, of the rock salt structure type.
˚
atoms in an average distance of 1.945 A. These TeO octa-
Regarding the layered nature of the crystal structure, it
is not self-evident to find a relationship to the α-NaFeO2
structure type here. Normally, one would expect the de-
6
hedra are isolated from each other and are linked via cop-
per atoms, which are situated in a twisted square coordi-
nation of oxygen atoms. The CuO squares share one com-
lafossite, CuFeO , structure type to occur [7, 8]. Here, our
4
2
mon edge and two vertices with the TeO octahedra, as is
former observations on layered silver oxides containing Sn,
Pb, Tl [9, 17] that, with increasing size of the octahedra
forming the [MO ]-slabs, the AgO dumbbells prefer a tilted
6
shown in Figure 1. The dihedral angle of the four square
iv
ii
i
ligands (O(2)-O(3) -O(3) -O(2) ) is about 19°, together with
2
2
˚
two more oxygen atoms at longer distances of 2.489 A (dot-
orientation with respect to the layer plane, is confirmed.
10
10
ted lines in Fig. 1) a distorted octahedral 4ϩ2 oxygen coor-
No short Ag-Ag separations indicative for d - d inter-
VI
dination results. The linkage of TeO and CuO
groups
actions are present in Ag CuTeO . Edge sharing Te O
6
4ϩ2
4
6
6
II
results in infinite chains extending along [001] as is illus-
trated in Figure 2. The chains are interconnected by Ag(1)
octahedra and Cu O squares are also known e.g. from Cu-
4
TeO [23].
4
Z. Anorg. Allg. Chem. 2007, 231Ϫ234
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
233

W. Klein, J. Curda, M. Jansen
4 6
Fig. 5 Temperature dependence of mean resisitivity of Ag CuTeO .
Acknowledgements. The authors would like to thank Dr. J. Nuss for
recording the single crystal data, and G. Siegle and E. Bruecher for
conductivity and magnetic measurements.
Fig. 3 Crystal structure of Ag
4
CuTeO
6
, view emphasizing the re-
octahedra,
lationship to the α-NaFeO structure type, with TeO
2
6
Cu and Ag(1) in distorted square planar, and Ag(2)/Ag(3) in appro-
ximately linear coordination by oxygen atoms.
References
[
[
[
[
1] S. N. Putilin, E. V. Antipov, O. Chmaissem, M. Marezio, Nat-
ure 1993, 362, 226.
2] M. J. Davis, M. D. Smith, K. E. Stitzer, H.-C. zur Loye, J.
Alloys Compd. 2003, 351, 95.
3] K. M. Mogare, K. Friese, W. Klein, M. Jansen, Z. Anorg. Allg.
Chem. 2004, 630, 547.
4] S. Ahlert, W. Klein, O. Jepsen, O. Gunnarsson, O. K.
Andersen, M. Jansen, Angew. Chem. 2003, 115, 4458, Angew.
Chem. Int. Ed. 2003, 42, 4322.
[5] C. Linke, M. Jansen, J. Solid State Chem. 1997, 134, 17.
[6] W. Klein, M. Jansen, Acta Crystallogr. 2005, C61, i1.
[7] G. Brachtel, M. Jansen, Cryst. Struct. Commun. 1981, 10, 173.
[8] B. U. Koehler, M. Jansen, J. Solid State Chem. 1987, 71, 566.
[9] M. Jansen, M. Bortz, K. Heidebrecht, Z. Kristallogr. 1989,
186, 147.
[
[
10] M. Bortz, M. Jansen, Z. Anorg. Allg. Chem. 1993, 619, 1446.
11] M. Jansen, S. Deibele, Z. Anorg. Allg. Chem. 1996, 622,
539Ϫ542.
[
[
12] W. Klein, J. Curda, M. Jansen, Z. Anorg. Allg. Chem. manu-
script in preparation.
13] W. Klein, J. Curda, E.-M. Peters, M. Jansen, Z. Anorg. Allg.
Chem. 2005, 631, 723.
Fig. 4 Temperature dependence of the molar magnetic susceptibi-
lity and its inverse of Ag
4 6
CuTeO . Parameters used for the Curie-
Weiss fit are given in the insert.
[
[
14] M. Weil, Acta Crystallogr. 2005, C61, i103.
15] W. Klein, J. Curda, E.-M. Peters, M. Jansen, Z. Anorg. Allg.
Chem. 2005, 631, 2893.
Ag CuTeO follows the Curie-Weiss law in the tempera-
[16] W. Klein, J. Curda, E.-M. Peters, M. Jansen, Z. Anorg. Allg.
Chem. 2006, 632, 1508.
[17] C. Linke, M. Jansen, Z. Anorg. Allg. Chem. 1997, 623, 1441.
4
6
ture range of 7-300 K, see Figure 4. This result is docu-
1
menting that the spin / sites are rather efficiently isolated.
2
[
18] SADABS, Bruker AXS Inc., Madison, WI, 1998.
[19] SHELXTL Version 6.10, Bruker AXS Inc., Madison, WI,
000.
The resulting magnetic moment of 1.86 µ is as expected for
B
2
ϩ
Cu , showing some significant orbital contribution. The
electronic conductivity shows a remarkable transition from
a semiconducting temperature characteristic at low tem-
peratures and a metallic one at higher temperatures, with
the maximum of conductivity at 75 K, see Figure 5.
Noteworthy this semiconductor to metal transition is not
reflected in the temperature dependence of the magnetic
susceptibility.
2
[20] K. Adelsberger, J. Curda, S. Vensky, M. Jansen, J. Solid State
Chem. 2001, 158, 82.
[
[
21] F. M. Chang, M. Jansen, Rev. Chim. Min. 1986, 23, 49.
22] F. M. Chang, M. Jansen, Angew. Chem. 1984, 96, 902; Angew.
Chem. Int. Ed. Engl. 1984, 23, 906.
[23] L. Falck, O. Lindqvist, W. Mark, Acta Crystallogr. 1978,
B34, 1450.
234
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Z. Anorg. Allg. Chem. 2007, 231Ϫ234