Condensed double-chain cluster complexes with seven-coordinate endohedral iridium atoms in {Ir2Gd5}Br5

Article abstract of DOI:10.1002/zaac.201200100

The new condensed double-chain cluster complex compound {Ir ₂Gd₅}Br₅ was obtained from a reaction of GdBr₃ with metallic gadolinium and iridium at elevated temperatures. The thin black needles crystallize with the orthorhombic crystal system, space group Pnma(no. 62); a = 1255.4(1) pm, b = 414.05(3) pm, c = 2633.8(3) pm,Z = 4, R₁/wR₂ = 0.0504/0.0346 for all data. Monocapped trigonal prisms of gadolinium atoms with endohedral iridium atoms are connected by common rectangular faces to chains and further by edges to double chains, which form a herringbone arrangement. The double chains are coordinated by bromido ligands and are connected in accord with the formulation {Ir₂Gd ₅}Br_4/2ⁱBr_2/3^i(e)Br _1/3^i(f)Br_2/2^i-i(e/f)Br _1/2^i-aBr_1/2^a-i. Copyright

Full text of DOI:10.1002/zaac.201200100

SHORT COMMUNICATION
DOI: 10.1002/zaac.201200100
Condensed Double-Chain Cluster Complexes with Seven-Coordinate
Endohedral Iridium Atoms in {Ir Gd }Br
2
5
5
[a]
*[a]
Matthias Brühmann and Gerd Meyer
Dedicated to Dr. habil. Werner Hanke on the Occasion of His 80th Birthday
Keywords: Cluster complexes; Crystal structure; Iridium; Gadolinium; Bromide
Abstract. The new condensed double-chain cluster complex compound
Ir Gd }Br was obtained from a reaction of GdBr with metallic gado-
linium and iridium at elevated temperatures. The thin black needles crys-
of gadolinium atoms with endohedral iridium atoms are connected by
common rectangular faces to chains and further by edges to double
chains, which form a herringbone arrangement. The double chains are
{
2
5
5
3
tallize with the orthorhombic crystal system, space group Pnma coordinated by bromido ligands and are connected in accord with the
i
i(e)
i(f)
i–i(e/f)
i–a
a–i
(
no. 62); a = 1255.4(1) pm, b = 414.05(3) pm, c = 2633.8(3) pm, formulation {Ir
2
Gd
5
}Br4/2 Br2/3 Br1/3 Br2/2
Br1/2 Br1/2 .
Z = 4, R /wR = 0.0504/0.0346 for all data. Monocapped trigonal prisms
1
2
Introduction
Results and Discussion
Thin black needle-shaped crystals of {Ir Gd }Br were ob-
2
5
5
In contrast to group 5 and 6 elements, for example niobium
and molybdenum, the valence-electron poor group 3 (rare-
earth) elements (R = Sc, Y, La, Ce–Lu) tend to form condensed
clusters with endohedral atoms (or small atom groups).[
tained by a comproportionation reaction of gadolinium tribro-
mide and gadolinium metal in the presence of metallic iridium
in an arc-welded tantalum tube by annealing the sample at
1–3]
9
10 °C for 12 days.
–
+
The endohedral atom Z contributes electrons to polar Z–R (δ δ )
{
Ir Gd }Br crystallizes in the orthorhombic space group
2
5
5
bonding.[ The condensation of clusters has the advantage that Pnma with lattice constants of a = 1255.4(1) pm, b =
a lesser number of negatively polarized (charged) ligands are 414.05(3) pm and c = 2633.8(3) pm, Z = 4. The crystal struc-
needed to complete the condensed cluster complex compound, ture contains double cluster chains of monocapped trigonal
4]
{
Z R }X .
gadolinium prisms connected (“condensed”) by common rec-
The majority of cluster complexes are derived from octahe- tangular faces. The {IrGd } prisms are centered by two crystal-
lographically distinguishable endohedral iridium atoms (Ir1,
x
y
z
7
dral clusters {ZR }. There are, however, an increasing number
6
Ir2) (Figure 1). Internuclear distances within the {IrGd } poly-
hedra range from 277.06(7) to 351.6(1) pm (Ir1; average
of cluster complexes with seven- or eight-coordinate endohed-
ral atoms Z. The coordination polyhedra are (distorted) mono-
capped trigonal prisms (coordination number of Z: CN = 7),
7
295.3 pm) and from 273.92(7) to 320.1(1) pm (Ir2; 292.6 pm),
[5]
respectively. As a consequence of the increased coordination
number, these are considerably longer than in octahedral clus-
ter complexes, for example in {IrGd }Br (ϽdϾ = 271.0 pm).
as for example in {RuPr }Cl , as well as square antiprisms
3
3
and cubes, as for example in {Os Lu }I (CN = 8).[
6]
5
20 24
6
10
The system Ir/Gd/Br appears to be rich of compounds: So
far we have grown crystals and determined the crystal struc-
tures of {IrGd }Br (X/R = 1.67; isolated octahedra)[ and
The average internuclear Gd–Ir–Gd angles between apical and
7]
6
10
{
Ir Gd }Br (X/R = 1.36; trimer of octahedra sharing
3
11
8]
15
[
edges). We now add {Ir Gd }Br (X/R = 1), which is, to
2
5
5
date, the most condensed cluster compound within the Ir/Gd/Br
system.
*
Prof. Dr. G. Meyer
Fax: +49-221-470-5083
E-Mail: gerd.meyer@uni-koeln.de
[
a] Department für Chemie, Institut für Anorganische Chemie
Universität zu Köln
Greinstraße 6
Figure 1. The two crystallographically independent {IrGd
in {Ir Gd }Br
7
} polyhedra
1257
50939 Köln, Germany
2
5
5
.
Z. Anorg. Allg. Chem. 2012, 638, (9), 1257–1260
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

M. Brühmann, G. Meyer
SHORT COMMUNICATION
Figure 2. Cluster double chains as observed in the crystal structure of {Ir
2
Gd
5
}Br
5
(left) and their view down [010] (right). The shortest
internuclear Ir–Ir distances of 301.75(6) pm are shown as dashed lines. Condensation of two single chains is depicted by light gray edges.
opposing gadolinium atoms in the metal polyhedra amount to indicate increased homoatomic bonding interactions within the
1
47.6° (Ir1) and 143.8° (Ir2) and deviate considerably from metal cluster framework in {Ir Gd }Br .
2 5 5
basal Gd–Ir–Gd angles of 166.6° (Ir1) and 155.1° (Ir2). Homo-
atomic Gd–Gd distances in the cluster framework range from
3
{
57.3(1) to 414.05(3) pm, on the average 379.2 pm for the
Ir(1)Gd } and 375.1 pm for the {Ir(2)Gd } polyhedron.
7
7
Condensation steps are the connection of {Ir(1)Gd } and
7
{
Ir(2)Gd } polyhedra by common rectangular faces to
7
{
Ir Gd } dimers, further to single cluster chains {Ir Gd } and,
2
10
2
6
finally, to double chains {Ir Gd } (Figure 2). The double
2
5
chains run parallel to the shortest axis, b = 414.05(3) pm.
There is a remarkable displacement of the iridium atoms out
of the basal cluster planes indicated by short (diagonal) Ir1–
Ir2 distances of 301.75(6) pm (Figure 2). Longer internuclear
Ir–Ir distances of 414.05(3) pm are located between neigh-
boring iridium atoms parallel to the chain alignment and
thereby correspond to the value of the crystallographic b axis.
The cluster chains are surrounded by μ -coordinating outer
1
a
bromido ligands (Br ) together with μ - and μ -coordinating
2
3
e
f
inner ligands capping edges (Br ) and faces (Br ). All bromido
ligands have bridging functions between adjacent cluster
chains with an average Gd–Br distance amounting to
306.9 pm. According to the Schäfer/Schnering nomenclature,
the inter-cluster connection might be addressed as
Ir Gd }Br Br2/3i(e)Br1/3 Br2/2i–i(e/f)Br1/2i–aBr1/2 . The i–i
i
i(f)
a–i
{
2 5 4/2
connection exclusively occurs parallel to the crystallographic
a axis, whereas bridging to neighboring chains along the c axis
is solely realized by i–a and a–i connections (Figure 3, top).
Thereby each column is linked to six neighboring chains and
thus exhibits a pseudo hexagonal, herringbone type arrange-
ment of rods as the structural packing motif (Figure 3, bottom).
The novel cluster complex bromide {Ir Gd }Br is closely
2
5
5
[5]
related to orthorhombic {RuPr }Cl , whose structure fea-
3
3
tures single chains of monocapped trigonal prisms centered by
endohedral ruthenium atoms. Scaled to one endohedral atom,
both compounds have the same number of 14 cluster based
electrons. {Ir Gd }Br therefore is a higher condensed variant
2
5
5
of {RuPr }Cl = {Ru Pr }Cl . Both compounds are one-di-
3
3
2
6
6
Figure 3. Inter-cluster connection of the cluster double chains in
Ir Gd }Br (top) and pseudo-hexagonal herringbone packing of the
distances of 302 pm vs. Ru–Ru distances of 308 pm. This may columns viewed down [010] (bottom).
mensional polar intermetallics with shortest internuclear Ir–Ir
{
2
5
5
1
258
www.zaac.wiley-vch.de
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 1257–1260

2 5 5
Condensed Double-Chain Cluster Complex {Ir Gd }Br
Leopoldshafen, Germany (Fax: +49-7247-808-666; E-Mail:
crysdata@fiz-karlsruhe.de, http://www.fiz-karlsruhe.de/request for
Conclusions
After {IrGd }Br and {Ir Gd }Br , a third compound, deposited data.html) on quoting the depository number CSD-424270
6
10
3
11
15
2 5 5
for {Ir Gd }Br .
{
Ir Gd }Br , could be detected in the Ir/Gd/Br system. It ap-
2 5 5
pears that it exists only at fairly low temperatures. The
thin black needles exhibit a condensed double-chain cluster
complex structure with seven-coordinate endohedral iridium
atoms.
Crystal Data for {Ir
2
Gd
5 5
}Br : Orthorhombic, space group Pnma (no.
6
1
2); a = 1255.4(1) pm, b = 414.05(3) pm, c = 2633.8(3) pm, V =
369.1(2)ϫ10 pm ; Z = 4; 1.55° Ͻ θ Ͻ 27.07°; Mo-K radiation
α
6
3
(
graphite monochromator, λ = 71.073 pm); T = 293(2) K; F(000) =
–
1
2596; μ = 57.762 mm ; 9250 reflections measured, 1520 unique, 1205
observed. Rint = 0.0738, R
0.0504/0.0346 [all data]; Goodness of fit on F = 0.693.
1
/wR = 0.0211/0.0323 [I Ͼ 2σ(I )] and
2
o
0
2
Experimental Section
Synthesis: Due to the high sensitivity of starting materials and prod-
ucts towards oxygen and moisture, all manipulations were carried out
under dry box conditions (MBraun, Garching, Germany; nitrogen at-
Acknowledgements
mosphere with partial pressures of
O Ͻ 0.5 ppm).
2
O Ͻ 1 ppm and of
We gratefully acknowledge support by the Deutsche Forschungsge-
meinschaft (DFG) through the framework of Sonderforschungsbereich
H
2
6
08 (Komplexe Übergangsmetallverbindungen mit Spin- und La-
2 5 5
Starting materials for the synthesis of {Ir Gd }Br were chips of
dungsfreiheitsgraden und Unordnung).
gadolinium metal (Chempur, Karlsruhe, Germany, 99.9%) and
iridium powder (Chempur, Karlsruhe, Germany, 99.9%), which were
used as purchased. Gadolinium tribromide was synthesized accord-
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5
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[
[
[
11]
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12]
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[14]
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1
(
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Z. Anorg. Allg. Chem. 2012, 1257–1260
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1259

M. Brühmann, G. Meyer
SHORT COMMUNICATION
3
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Received: March 03, 2012
Published Online: June 11, 2012
1
260
www.zaac.wiley-vch.de
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 1257–1260