The Starting Members of the Series Pr4n+2(C2) nBr5n+5(n = 1, 2, 3)

Article abstract of DOI:10.1515/znb-2009-0808

The compounds Pr₆(C₂)Br₁₀, Pr ₁₀(C₂)₂Br₁₅ and Pr ₁₄(C₂)3Br₂₀ were prepared from PrBr₃ and the appropriate amounts of Pr and C and char

Full text of DOI:10.1515/znb-2009-0808

The Starting Members of the Series Pr4n+2(C2)nBr5n+5 (n = 1, 2, 3)
Manuel Christian Schaloskea, Hansju¨rgen Mattauscha, Viola Duppela, Lorenz Kienleb,
and Arndt Simona
a Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
b Technische Fakulta¨t, Institut fu¨r Materialwissenschaft, Christian-Albrechts-Universita¨t zu Kiel,
Kaiserstraße 2, 24143 Kiel, Germany
Reprint requests to Prof. Dr. Dr. h. c. mult. Arndt Simon. Fax: +49-(711)-689-1091.
E-mail: A.Simon@fkf.mpg.de
Z. Naturforsch. 2009, 64b, 922 – 928; received June 4, 2009
The compounds Pr6(C2)Br10, Pr10(C2)2Br15 and Pr14(C2)3Br20 were prepared from PrBr3 and the
appropriate amounts of Pr and C and characterized by X-ray structure analyses of single crystals. All
¯
three compounds crystallize in space group P1 with lat◦tice parameters a = 7.571(2), b = 9.004(2), c =
˚
9.062(2) A, α = 108.57(3), β = 97.77(3), γ = 106.28(3) for P◦r6(C2)Br10; a = 9.098(2), b = 10.127(2),
˚
c = 10.965(2) A, α = 70.38(3), β = 66.31(3), γ = 70.84(3) for Pr10◦(C2)2Br15; a = 9.054(2), b =
˚
10.935(2), c = 13.352(3) A, α = 86.27(3), β = 72.57(3), γ = 66.88(3) for Pr14(C2)3Br20. They are
members of a general series Ln4n+2(C2)nBr5n+5 and isostructural with the corresponding iodides
known for Ln = La, Ce, Pr. Pr6(C2)Br10 was further characterized via transmission electron mi-
croscopy techniques.
Key words: Praseodymium, Bromide, Cluster, TEM
Introduction
[14], Pr10(C2)2Br16 [15], Gd10(C2)2Cl17, and Gd10
(C2)2Cl18 [16].
The early recognized cluster condensation in the un-
usual structure of NbO [1] turned out to be an ordering
principle for a plethora of structures of metal-rich tran-
sition metal (M) compounds with p elements (X) [2, 3].
Beside others, especially M6X8 and M6X12 clusters oc-
cur which are connected via the vertices, edges or faces
of the M6 octahedra forming dimers, oligomers and as-
semblies of higher dimensionality. Moreover this con-
cept proved its value for the exploration of new sub-
stance groups, i. e. the metal-rich rare-earths halides
containing empty or occupied, discrete or condensed
clusters [4 – 6].
Regarding the known examples of one-dimensional-
ly linked structures, a homologous series with the gen-
eral formula Ln4n+2(C2)nX5n+5 (Ln = lanthanide) has
been established [7]. It starts with Ln6(C2)I10 (Ln = La
[8], Ce, Pr [9]) exhibiting isolated Ln6 octahedra, fol-
lowed by Ln10(C2)2I15 (Ln = La [8]) and Ln14(C2)3I20
(Ln = La, Ce [7, 10], Pr [11, 12]), which contain edge-
sharing double and triple octahedra, respectively. An
infinite chain of clusters, Ln4(C2)I5, is also known for
La, Ce and Pr [13].
In this contribution we describe the preparation and
crystal structures of the starting members of the series
containing Br as the halogen component. In detail the
compounds Pr6(C2)Br10, Pr10(C2)2Br15 and Pr14(C2)3
Br20 are presented.
Experimental Section
Synthesis
Praseodymium metal (pieces of 1 – 3 mm edge length,
sublimed, 99.99 %, Alfa-Aesar), PrBr3 and graphite powder
(pure, Aldrich) were used as starting materials for synthe-
ses. PrBr3 was synthesized from the reaction of Pr6O11 with
NH4Br in aqueous HBr and heated to dryness [17]. The raw
product was purified twice by sublimation in a Ta tube at
◦
900 C / 10−4 torr. All handling was carried out under Ar
atmosphere either in a glovebox (M. Braun) or through the
Schlenk technique.
1.0 g of the mixture of the starting materials was arc-
sealed in Ta tubes under Ar atmosphere. Then the Ta tubes
were enclosed in silica glass ampoules under vacuum.
The ampoules were annealed for several days at different
temperatures and then quenched in water.
By now, several different structures based on
Pr (C )Br : A mixture of Pr : PrBr3 : C in a molar ratio
6
2
10
double-octahedra are known, namely Gd10(C2)2I16 of 4 : 5 : 3 was annealed for 17 days at 850 ◦C. Black polyhe-
c
0932–0776 / 09 / 0800–0922 $ 06.00 ꢀ 2009 Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com
Unauthenticated
Download Date | 11/17/19 9:45 PM

M. C. Schaloske et al. · The Starting Members of the Series Pr4n+2(C2)nBr5n+5 (n = 1, 2, 3)
923
Table 1. Crystal data and structure refinement of Pr6(C2)Br10, Pr10(C2)2Br15 and Pr14(C2)3Br20
.
Sum formula
Pr6(C2)Br10
1668.58
black, polyhedral
293(2)
Pr10(C2)2Br15
2655.79
silver, polyhedral
293(2)
Pr14(C2)3Br20
3643.00
black, polyhedral
293(2)
Formula weight, g mol−1
Color, habitus
Temperature, K
Wavelength; radiation, A
˚
AgKα ; 0.56086
triclinic
MoKα ; 0.71073
triclinic
MoKα ; 0.71073
triclinic
Crystal system
Space group
¯
¯
¯
P1
P1
P1
˚
a, A
7.571(2)
9.004(2)
9.062(2)
108.57(3)
97.77(3)
106.28(3)
544.8(2)
1
9.098(2)
10.127(2)
10.965(2)
70.38(3)
66.31(3)
70.84(3)
9.054(2)
10.935(2)
13.352(3)
86.27(3)
72.57(3)
66.88(3)
˚
b, A
˚
c, A
α, deg
β, deg
γ, deg
3
3
3
˚
˚
˚
Volume, A
849.3(3) A
1
1157.8(4) A
Formula units per unit cell
Density (calcd.), g cm−3
Absorption coefficient, mm−1
F(000)
1
5.09
16.8
716
5.19
31.7
1139
5.23
31.7
1562
Crystal dimensions, mm3
Diffractometer
0.24×0.16×0.12
IPDS I (Stoe, Darmstadt)
2.60◦ ≤ ϑ ≤ 27.50◦
−12 ≤ h ≤ 12, −14 ≤ k ≤ 14,
−14 ≤ l ≤ 14
18628 / 4716
0.10×0.08×0.06
IPDS II (Stoe, Darmstadt)
3.36◦ ≤ ϑ ≤ 24.99◦
−10 ≤ h ≤ 10, −12 ≤ k ≤ 12,
−13 ≤ l ≤ 13
0.18×0.14×0.12
IPDS II (Stoe, Darmstadt)
2.51◦ ≤ ϑ ≤ 28.50◦
Measured ϑ range
Index ranges
−12 ≤ h ≤ 12, −14 ≤ k ≤ 14,
−17 ≤ l ≤ 17
Measured reflections /
independent
10609 / 2973
20850 / 5863
Absorption correction
Max. / min. transmission
Structure solution
numerical [24]
0.320 / 0.169
Direct Methods [25]
full-matrix least-squares
on F2 [26]
numerical [24]
0.116 / 0.032
Direct Methods [25]
full-matrix least-squares
on F2 [26]
numerical [24]
0.157 / 0.065
Direct Methods [25]
full-matrix least-squares
on F2 [26]
Structure refinement
Data/ ref. parameters
R1 / wR2 [I ≥ 2 σ(I)]
R1 / wR2 (all data)
4716 / 83
2973 / 134
5863 / 167
0.044 / 0.108
0.060 / 0.113
1.18
3.12 / −3.45
0.038 / 0.058
0.0525 / 0.060
1.20
1.27 / −1.33
0.057 / 0.111
0.089 / 0.120
1.01
4.15 / −3.05
Goodness-of-fit on F2
−3
˚
Final Fourier residuals, e A
dral single crystals were observed, which cleave layer-wise. out under dry Ar with the aid of a special device [18, 19].
The yield was about 90 %. A perforated carbon/copper net served as support for the
Pr (C ) Br : Silvery crystals were obtained by anneal- crystallites. Simulations of HRTEM images (multislice for-
10 2 2 15
◦
ing Pr : PrBr3 : C in a molar ratio of 5 : 5 : 4 at 835 C (24 d) malism) and of SAED patterns (kinematical approximation)
with a yield of about 80 %.
were calculated with the EMS program package [20] (spread
˚
Pr (C ) Br : Black crystals with metallic luster, cleav- of defocus: 70 A, illumination semiangle: 1.2 mrad). All im-
14 2 3 20
ing layer-wise, were obtained after annealing a mixture of ages were recorded with a Gatan Multiscan CCD camera and
◦
Pr : PrBr3 : C in a molar ratio of 11 : 10 : 9 at 850 C for 23 evaluated (including Fourier filtering) with the program DIG-
days with a yield of about 80 %.
ITAL MICROGRAPH 3.6.1 (Gatan). All HRTEM images were
In all cases Pr4CxBr5 and/or Pr4(C2)1−xBr5 [13], respec- filtered after Fourier transformation by using a suitable band-
tively, were formed as by-products. In other syntheses, Pr6- pass mask.
(C2)Br10 and Pr10(C2)2Br15 were coexisting, but in no case
X-Ray structure investigation
together with Pr14(C2)3Br20
.
The reaction products were ground to fine powders un-
der Ar atmosphere and sealed in glass capillaries for phase
Electron microscopy
identification by a modified Guinier technique [21] (CuKα 1
:
˚
˚
HRTEM and SAED (selected area electron diffraction) λ = 1.54056 A; internal standard Si with a = 5.43035 A; Fu-
were performed with a Philips CM30 ST microscope jifilm BAS-5000 image plate system). Single crystals were
(300 kV, LaB6 cathode, CS = 1.15 mm). All manipulations transferred to glass capillaries under Na-dried petroleum and
for the preparation and transfer of the samples were carried sealed under Ar atmosphere. They were first examined by
Unauthenticated
Download Date | 11/17/19 9:45 PM

924
M. C. Schaloske et al. · The Starting Members of the Series Pr4n+2(C2)nBr5n+5 (n = 1, 2, 3)
˚
Table 3. Shortest distances (A), calculated on the basis of the
Table 2. Atomic coordinates and displacement parameters (in
A ). Ueq is defined as one third of the trace of the orthogo-
nalized Uij tensor.
2
˚
X-ray single crystal investigation.
Pr6(C2)Br10
Pr1 Pr2 3.510(1)
Pr2 3.561(1)
Pr3 3.863(1)
Pr3 3.931(2)
Br1 3.114(1)
Br1 2.982(2)
Br2 3.085(1)
Br2 3.133(1)
Br3 2.944(1)
Br4 2.940(1)
Br4 3.108(1)
Br5 2.926(2)
C1 2.609(6)
C1 2.611(6)
Atom
Pr6(C2)Br10
x/a
y/b
z/c
Ueq
Pr1
Pr2
Pr3
Br1
Br2
Br3
Br4
Br5
C1
0.1138(1)
0.0434(1)
0.2853(1)
0.1598(1)
0.0867(1)
0.1820(1)
−0.2767(1)
0.3750(1)
0.4817(1)
0.0353(7)
−0.2336(1)
0.0852(1)
0.2078(1)
0.4720(1)
−0.0858(1)
−0.3675(1)
−0.1800(1)
0.2863(1)
0.0483(7)
0.0095(1)
0.0107(1)
0.0118(1)
0.0234(2)
0.0143(1)
0.0146(1)
0.0235(2)
0.0257(2)
0.010(1)
−0.0258(1)
0.3973(1)
0.2590(1)
0.5459(1)
0.1742(1)
0.0925(1)
0.3590(1)
0.0963(9)
Br3 2.941(1) Pr3 Br1 2.925(1)
Br4 2.923(1)
Br2 3.067(1)
Br2 3.095(1)
Br3 3.094(1)
Br5 2.864(1)
C1 2.277(6)
C1
C1
2.588(6)
2.598(6)
Pr2 Pr3 3.826(1)
Pr3 3.988(2)
Pr10(C2)2Br15
Pr1
Pr2
Pr3
Pr4
Pr5
Br1
Br2
Br3
Br4
Br5
Br6
Br7
Br8
C1
0.0804(1)
0.1797(1)
0.1028(1)
0.5402(1)
0.4301(1)
−0.2479(1)
0.2708(1)
−0.0926(1)
0.4434(1)
0.3685(1)
0.1653(1)
0.0301(1)
−0.1851(1)
0.8849(1)
0.2659(1)
0.6408(1)
0.0457(1)
0.8306(1)
0.8151(1)
0.0621(1)
0.7003(1)
0.4155(1)
0.2226(1)
0.6411(1)
0.4635(1)
0
0.0140(1)
0.0120(1)
0.0136(1)
0.0110(1)
0.0117(1)
0.0184(2)
0.0184(2)
0.0187(2)
0.0251(3)
0.0233(3)
0.0172(2)
0.0253(3)
0.0288(4)
0.014(2)
C1 C1 1.44(1)
0.0277(1)
0.2472(1)
0.1713(1)
0.3357(1)
0.3906(1)
0.2354(1)
−0.0557(1)
0.4486(1)
0.3385(1)
0.2606(1)
0.1346(2)
Pr10(C2)2Br15
Pr1 Pr1 4.014(2)
Pr2 3.840(1)
Pr4 3.973(1)
Pr4 4.015(2)
Pr5 3.845(2)
Br6 2.996(2)
Br7 3.002(2)
Br7 3.119(2)
C1 2.593(9)
C2 2.574(9)
Br1 3.090(2)
Br3 3.109(2)
Br5 3.077(2)
Br8 3.105(9)
C1
C1
C2
C2
2.655(9)
2.683(10)
2.677(10)
2.713(9)
Br1 2.984(2) Pr3 Pr4 3.979(2)
Br2 3.057(2)
Br2 3.069(2)
Br3 2.996(2)
Br6 3.114(2)
Pr4 4.019(1)
Pr5 3.882(1)
Br1 2.994(2) Pr5 Br2 3.103(2)
Br3 2.980(2)
Br4 2.971(2)
Br4 3.105(2)
Br7 2.943(2)
C2 2.29(1)
Br4 3.002(2)
Br5 3.120(1)
Br6 2.943(2)
Br8 2.957(1)
1
1
/2
/2
C1
2.29(1)
−0.0435(12)
0.2959(11) 0.0600(11)
0.3591(10) 0.1742(11)
Pr2 Pr3 3.856(2)
Pr4 3.669(2)
C2
−0.1216(12)
0.012(2)
Pr14(C2)3Br20
Pr5 3.576(1)
C1
C2
2.58(1)
2.574(9)
1.42(1)
Pr1
Pr2
Pr3
Pr4
Pr5
Pr6
Pr7
Br1
Br2
Br3
Br4
Br5
Br6
Br7
Br8
Br9
Br10
C1
0.4065(1)
0.2180(1)
0.3820(1)
0.4516(1)
0.7586(1)
0.4145(1)
0.7090(1)
−0.0617(1)
0.4546(1)
0.6373(2)
0.2523(2)
0.7228(1)
0.4207(2)
0.1898(2)
0.0681(2)
0.1018(2)
0.0230(2)
0.1544(1)
0.5784(1)
0.8208(1)
0.9211(1)
0.8993(1)
0.3612(1)
0.3113(1)
0.1686(1)
0.4347(1)
0.7020(1)
0.6251(1)
0.8300(1)
0.8781(1)
0.0356(1)
0.3669(1)
0.9059(1)
0.7760(2)
0.4815(1)
0.0104(2)
0.0101(2)
0.0096(2)
0.0131(2)
0.0137(2)
0.0105(2)
0.0128(2)
0.0168(3)
0.0186(3)
0.0248(4)
0.0180(3)
0.0256(3)
0.0162(3)
0.0259(4)
0.0183(3)
0.0248(3)
0.0159(3)
0.008(2)
Br2 3.099(2) Pr4 Pr4 3.375(1)
Br5 2.918(1)
Pr14(C2)3Br20
Pr1 Pr2 3.718(2)
Pr5 3.828(2)
Pr6 3.587(1)
Pr7 3.778(2)
Br1 3.098(2)
Br3 2.932(2)
Br7 3.001(2)
Br7 3.123(2)
0.0585(1)
0.3137(1)
−0.0721(1)
0.6990(1)
0.3193(1)
0.5322(1)
0.3300(2)
−0.0627(2)
0.0543(2)
0.2855(2)
−0.3180(2)
0.4440(2)
0.4778(3)
0.1078(2)
−0.1767(2)
0.7735(2)
0.3944(15)
0.0202(17)
0.3576(14)
Pr5 3.692(2) C1 C2
Br4 3.076(2)
Br5 3.092(2)
Br5 3.120(2)
Br4 2.985(2)
Br10 3.110(2)
C3
2.27(1)
Br6 3.128(2) Pr6 Pr1 3.587(1)
C1 2.68(1)
C2 2.66(1)
C2 2.66(1)
C3 2.66(1)
Pr3 3.701(2)
Pr7 3.822(2)
Br1 3.123(2)
Br3 3.089(2)
Br5 2.984(2)
Br9 3.016(2)
Br10 2.959(2)
Br10 2.988(2) Pr4 Pr2 3.966(2)
C1
C3
2.58(1)
2.60(1)
Pr3 3.998(2)
Pr5 3.986(2)
Br2 2.990(2)
Br4 2.958(2)
Pr2 Pr3 3.328(1)
Pr3 3.949(2)
Pr4 3.930(2)
Br2 3.094(2)
Br3 3.070(2)
Br5 3.120(2)
C1
C3
2.58(1)
2.59(1)
Br6 3.038(2) Pr7 Pr1 3.778(2)
0.2701(12) 0.7672(9)
0.4374(13) 0.0222(10)
0.3914(11) 0.7214(9)
Br8 2.971(2)
Br9 3.184(2)
C2 2.26(1)
Pr2 4.009(2)
Pr3 4.068(2)
Pr6 3.822(2)
Br6 3.057(2)
Br6 3.138(2)
Br7 2.903(2)
Br8 2.966(2)
Br9 2.938(2)
C2
C3
0.013(2)
0.005(2)
Br8 3.108(2) Pr5 Pr1 3.828(2)
precession techniques before being characterized on a Stoe
IPDS image plate instrument.
C1
C2
C2
C3
2.67(1)
2.69(1)
2.71(1)
2.67(1)
Pr2 3.951(2)
Pr3 3.971(1)
Pr4 3.986(2)
Pr6 3.877(2)
Br1 3.042(2)
¯
All three compounds crystallize in space group P1 with
Z = 1. Cell parameters and parameters for data collection and
refinement are summarized in Table 1. Tables 2 and 3 contain
the atomic coordinates and short distances in the three crystal
structures.
Pr3 Pr2 3.949(2)
Pr4 3.850(2)
C1
2.30(1)
1.38(2)
1.41(3)
Br1 3.055(2) C1 C3
Br2 2.968(2) C2 C2
Pr6 3.701(2)
Unauthenticated
Download Date | 11/17/19 9:45 PM

M. C. Schaloske et al. · The Starting Members of the Series Pr4n+2(C2)nBr5n+5 (n = 1, 2, 3)
925
←− Fig. 1. Projections of the crystal structures of
a) Pr6(C2)Br10 along ca. [111], b) Pr10(C2)2Br15 along [001]
and c) Pr14(C2)3Br20 along [010]. The Br, Pr and C atoms are
illustrated as bright, grey and black spheres, respectively. Pr6
clusters as well as the cell edges are emphasized with their
contours.
a)
Further details of the crystal structure investigations
may be obtained from Fachinformationszentrum Karlsruhe,
76344 Eggenstein-Leopoldshafen, Germany (fax: +49-7247-
808-666; e-mail: crysdata@fiz-karlsruhe.de, http://www.fiz-
informationsdienste.de/en/DB/icsd/depot anforderung.html)
on quoting the deposition numbers CSD-420331 (Pr6(C2)-
Br10), CSD-420332 (Pr10(C2)2Br15), and CSD-420333
(Pr14(C2)3Br20).
Results
Within the homologous series Ln4n+2(C2)nX5n+5 the
compounds presented here comply with the first three
members, n = 1, 2 and 3. The standard setting of the
unit cell according to the lengths of the axes is cho-
sen, but in order to reach a better comparison, the stan-
dard setting of Pr6(C2)Br10 is changed via the matrix
(–1 –1 0 0 –1 0 0 0 1) resulting in a = 7.571(2), b =
b)
˚
10.009(2), c = 9.062(2) A, α = 67.13(3), β = 82.23(3),
γ = 59.72(3)◦.
˚
One axis then becomes almost exactly 10 A long,
˚
whereas it is approx. 10.9 A for the other two com-
pounds. One of the angles, 67◦, as well as one of the
˚
axes, 9.05– 9.09 A, is nearly identical in all three com-
pounds. Another axes is increased by approx. 2.5 A per
˚
additional octahedron in the cluster. The partly differ-
ent changes in the lattice parameters are caused by the
fact that the octahedra do not lie parallel to one axis
but in skewed positions in the cell. Nevertheless, some
relationships in the parameters are obvious concerning
common axes and similar angles.
c)
The crystal structures of the three compounds may
be depicted as an arrangement of shifted cluster rows,
whose sections consist of single or condensed double-
and triple-octahedra, respectively. In Figs. 1a – c these
structures are shown as projections along the axes of
˚
approx. 10.9 and 10.0 A, respectively, that relate to
different directions. The Br atoms are aligned in diag-
onal rows, interrupted by C2 dumbbells in perpendic-
ular orientation to these rows. These C2 units are each
surrounded by Ln6 octahedra. The latter are arranged
in alternating layers according to an A, B stacking, cf.
Figs. 2a – c.
The coordination of the Pr atoms by bridg-
ing Br atoms is equal to that of the corre-
Unauthenticated
Download Date | 11/17/19 9:45 PM

926
a)
M. C. Schaloske et al. · The Starting Members of the Series Pr4n+2(C2)nBr5n+5 (n = 1, 2, 3)
←− Fig. 2. Projections of the crystal structures of
a) Pr6(C2)Br10 along [121], b) Pr10(C2)2Br15 along ca.
[6 −10 3] and c) Pr14(C2)3Br20 along [001]. The Br, Pr and
C atoms are illustrated as bright, grey and black spheres, re-
spectively. Pr6 clusters as well as the cell edges are empha-
sized with their contours.
sponding La-I compounds and is further explained
in ref. [7].
Distances between Pr atoms lie in the range from
˚
3.33 to 4.07 A. The shortest ones are observed in the
waist, the connecting edge of the octahedra, and the
longest are those from the vertices to the waist. In con-
trast to the reduced oxomolybdates containing −empty
(n+3)
and discrete cluster anions [Mo4n+2O6n+4
]
with
only minor variations of the Mo–Mo distances [22], the
6−
repulsion between the highly charged interstitial C2
ions leads to a significant distortion of the Ln6 octahe-
dra, which has frequently been described earlier, e. g.
for the isostructural iodides. Additionally, the residual
valence electrons which are localized in the common
edge [23] enforce this effect. For Pr6(C2)Br10, with
only isolated octahedra, the distances vary only be-
b)
˚
tween 3.51 and 3.99 A. Pr–Br distances range from
˚
2.86 to 3.18 A for all three compounds. The C–C bond
˚
lengths with 1.39 to 1.44 A lie between those of usual
C–C single and double bonds (cf. Table 3).
Electron microscopy
The electron microscopic investigation was per-
formed on a heterogeneous sample composed of Pr10
(C2)2Br16 and Pr6(C2)Br10 with a ratio of ca. 60: 40.
The polyhedral crystals lay in different orientations
on the copper grid, thus images of multiple direc-
tions were recorded. A selection of suitable SAED
patterns is shown and discussed in the Addendum
(below).
c)
Due to the rapid amorphization of the crystals
caused by beam damage, HRTEM images could only
be taken along the [210] direction. These images, in-
cluding the simulation for two focus values, are pre-
sented in Fig. 3. For comparison, the crystal potential,
calculated on the basis of the X-ray model, as well as
the HRTEM simulation for the Scherzer focus (∆f =
−60 nm), are shown. In the potential representation
large dark spots represent the metal atoms in the struc-
ture, and smaller ones the Br atoms. The resulting sin-
gle octahedra are depicted with their contours. In the
HRTEM simulation at Scherzer focus one could de-
tect grey and bright areas within the black background.
Unauthenticated
Download Date | 11/17/19 9:45 PM

M. C. Schaloske et al. · The Starting Members of the Series Pr4n+2(C2)nBr5n+5 (n = 1, 2, 3)
927
Fig. 3. Representation of crystal potential (left) and simu-
lated HRTEM image (right, ∆ f = −60 nm, t = 4.6 nm) for
Pr6(C2)Br10 projected along [210] with the embedded clus-
ter contours. Experimental images with inserted simulations
(mid ∆ f = 55 nm, bottom ∆ f = −35 nm, t = 4.6 nm).
Fig. 4. Experimen-
tal SAED patterns
(left)
compared
with the simula-
tions (right) for six
different directions
The dark contrasts corresponding with high values of
the projected potential can be assigned to the Pr6 octa-
hedra. Residual dark contrasts that are forming rows
of Pr6(C2)Br10
.
can be assigned to the Br atoms. There, bright con-
trasts correlate with low values of the potential, i. e.
with the voids between the octahedra and the rows of
Br atoms.
The comparison of the simulation and the exper-
imental high-resolution images in the lower part of
Fig. 3 shows a good agreement of the contrasts. At
∆f = 55 nm the contrasts are completely inverted, but
agree also with the embedded simulation. With the
knowledge of the structural relation to the image, one
could easily comprehend the diagonal arrangement of
the single octahedra represented by strings of white
spots at this focus value, which correlate with the cor-
ners of the octahedra. Accordingly, the dark spots rep-
resent the cores of the octahedra. For ∆f = −35 nm a
contrast reversal occurs, and the dark spots now corre-
spond with the heavy atoms and are interpreted as the
corners of the octahedra.
Unauthenticated
Download Date | 11/17/19 9:45 PM

928
M. C. Schaloske et al. · The Starting Members of the Series Pr4n+2(C2)nBr5n+5 (n = 1, 2, 3)
Addendum
model derived from the X-ray data. Beside the obvious
inversion symmetry, no further symmetry elements are
Beside the [001] axes, in Fig. 4 some diagonal di-
rections are also depicted, whose SAED patterns all
show clear bright spots without any diffuse or elon-
gated reflections. Due to multiple scattering, the ob-
served intensities partly disagree with the simulations
on the right, which are calculated on the basis of the
observed. In some orientations additional spots occur
belonging to higher order Laue zones.
Acknowledgement
The authors are indebted to Dr. C. Hoch and H. Ga¨rttling for
single crystal X-ray investigations.
[1] H. Scha¨fer, H. G. Schnering, Angew. Chem. 1964, 76,
833.
[14] Hj. Mattausch, E. Warkentin, O. Oeckler, A. Simon,
Z. Anorg. Allg. Chem. 2000, 626, 2117.
[15] M. C. Schaloske, Hj. Mattausch, L. Kienle, A. Simon,
Z. Anorg. Allg. Chem. 2008, 634, 2246.
[2] A. Simon, Angew. Chem. 1981, 93, 23; Angew. Chem.,
Int. Ed. Engl. 1981, 20, 1.
[3] A. Simon, Angew. Chem. 1988, 100, 163; Angew.
Chem., Int. Ed. Engl. 1988, 27, 159.
[4] A. Simon, Hj. Mattausch, G. J. Miller, W. Bauhofer,
R. K. Kremer, Handbook on the Physics and Chemistry
of Rare Earth, Vol. 15, Elsevier Science Publ., Amster-
dam 1991, p. 191.
[16] A. Simon, E. Warkentin, R. Masse, Angew. Chem.
1981, 93, 1071; Angew. Chem., Int. Ed. Engl. 1981, 20,
1013.
[17] G. Meyer, P. Ax, Mater. Res. Bull. 1982, 17, 1447.
[18] P. Jeitschko, A. Simon, R. Ramlau, Hj. Mattausch, Eu-
rop. Microscopy Microanal. 1997, 46, 21.
[5] J. D. Corbett, J. Chem. Soc., Dalton Trans. 1996, 12,
575.
[6] G. Meyer, Chem. Rev. 1988, 88, 93.
[7] Hj. Mattausch, A. Simon, L. Kienle, C. Hoch,
C. Zheng, R. K. Kremer, Z. Anorg. Allg. Chem. 2006,
632, 1661.
[19] P. Jeitschko, A. Simon, R. Ramlau, Hj. Mattausch,
Z. Anorg. Allg. Chem. 1997, 623, 1447.
[20] P. A. Stadelmann, Ultramicroscopy 1987, 21, 131.
[21] A. Simon, J. Appl. Crystallogr. 1970, 3, 11.
[22] Hj. Mattausch, A. Simon, E.-M. Peters, Inorg. Chem.
1986, 25, 3428.
[8] Hj. Mattausch, C. Hoch, A. Simon, Z. Anorg. Allg.
Chem. 2005, 631, 1423.
[9] M. C. Schaloske, A. Simon, unpublished results.
[10] L. Kienle, Hj. Mattausch, A. Simon, Angew. Chem.
2006, 118, 8204; Angew. Chem. Int. Ed. 2006, 45,
8036.
[23] S. Satpathy, O. K. Andersen, Inorg. Chem. 1985, 24,
2604.
[24] X-RED32 (version 1.26), X-SHAPE2 (version 2.05),
Crystal Optimisation for Numerical Absorption Cor-
rection, Stoe & Cie. GmbH, Darmstadt (Germany)
2004.
[11] R. Wiglusz, I. Pantenburg, G. Meyer, Z. Kristallogr.
NCS 2007, 222, 9.
[12] L. Kienle, M. C. Schaloske, Hj. Mattausch, V. Duppel,
A. Simon, Solid State Sci. 2008, 10, 401.
[13] Hj. Mattausch, M. C. Schaloske, C. Hoch, C. Zheng,
A. Simon, Z. Anorg. Allg. Chem. 2008, 634, 491.
[25] G. M. Sheldrick, SHELXS-97, Program for the Solution
of Crystal Structures, University of Go¨ttingen, Go¨ttin-
gen (Germany) 1997.
[26] G. M. Sheldrick, SHELXL-97, Program for the Refine-
ment of Crystal Structures, University of Go¨ttingen,
Go¨ttingen (Germany) 1997. See also: G. M. Sheldrick,
Acta Crystallogr. 2008, A64, 112.
Unauthenticated
Download Date | 11/17/19 9:45 PM