The molecular solid Sc24C10I30: A truncated, hollow T4 supertetrahedron of iodine filled with a T3 supertetrahedron of scandium that encapsulates the adamantoid cluster Sc 4C10

Article abstract of DOI:10.1002/anie.200503914

(Figure Presented) Like a Russian doll: In the nanomolecule Sc ₂₄C₁₀I₃₀, an outer I₃₀ envelope (pink) surrounds a Sc₂₀ T3 supertetrahedron (blue), which is filled by a C₁₀ T2 supertetrahedron (gray), which, in turn, is filled by a Sc₄ T1 tetrahedron (light gray), containing two electrons in a four-center, two-electron bond.

Full text of DOI:10.1002/anie.200503914

Communications
I
0
.00 1.00
ScI
3
0.25
0.75
{
Sc C}I
Sc0.9 I2
7
12
{
Sc C }I
6 2 11
0.50
{Sc C }I
0.50
4
2
6
Sc24
10 30
C I
0.75
0.25
1
.00
0.00
1.00
0
.00
0.25
0.50
0.75
C
Sc
Figure 1. Compounds in the Sc/C/I system (binary C/I and Sc/C
compounds are omitted).
approximately 100 K. At low temperatures, the excess
3
+
À
À
electrons (according to 9” Sc 0.89I2 = (Sc ) & (I ) (e ) for
8
1
18
6
a hypothetical ninefold superstructure) are localized in
scandium 3d states, resulting in the presence of some divalent
2
+
scandium (Sc ), as revealed by the compoundꢀs well-resolved
[
2]
ESR spectrum. Excess electrons may also be used for ScÀSc
bonding, as evidenced by the rather short ScÀSc distance of
[
3]
3
28 pm in NaSc I and supported by band-structure calcu-
2 6
[
2,3]
lations.
The ScÀSc bonding and ScÀI antibonding inter-
[2]
actions must be finely tuned at the Fermi level, which
explains the enigmatic scandium deficiencies observed not
[
2,4]
Iodine Supertetrahedra
only in Sc I , but also in CsSc I , for example.
0.9 2 0.8 3
Excess electrons may not only be delocalized, as in
2
+
DOI: 10.1002/anie.200503914
metallic Sc I , or localized at the atoms (Sc , paramagnetic)
0.9 2
or in bonds, but may also be used by a third partner. This is, at
The Molecular Solid Sc C I : A Truncated,
3+
2
4
10 30
least in a simple (ionic) model, the case in Sc C I = (Sc ) -
4
2
6
4
Hollow T4 Supertetrahedron of Iodine Filled with
6À
À
[5]
(C
)(I ) . In this compound, in addition to Coulombic
2
6
a T3 Supertetrahedron of Scandium That
3+
À
Sc ÀI interactions, there are also strong covalent ScÀC and
Encapsulates the Adamantoid Cluster Sc C **
4
10
À
À
À
Sc Sc interactions, as revealed by the short Sc Sc and Sc C
distances of 302 and 200 pm, respectively. A similar picture
[
5]
holds for Sc C I , which bears one excess electron in this
Liesbet Jongen, Anja-Verena Mudring,* and
Gerd Meyer*
6
2 11
model.
In an attempt to produce Sc C I in pure form for physical
6
2 11
[
6]
measurements, we have now obtained Sc CI , a slightly
Dedicated to Professor John D. Corbett
on the occasion of his 80th birthday
2.4
3
more scandium-rich carbide iodide than Sc C I =^ Sc CI
3
4
2
6
2
[
5]
(
Figure 1). The new compound is better formulated as
Sc C I , as its solid-state structure is built from molecules of
2
4
10 30
3
There are two iodides of scandium (Figure 1), the rather
this composition. The large cubic unit cell (V= 16.943(3) nm
trivial insulator ScI and the scandium-deficient compound
at 293 K) contains eight crystallographically equivalent
3
[
1]
[7]
Sc I , which is metallic above and insulating below
Sc C I molecules. As one eighth of the unit-cell volume
0
.9
2
24 10 30
3
is 2.12 nm , and if a space filling of 70% is assumed, each
3
[
*] Dr. L. Jongen, Dr. A.-V. Mudring, Prof. Dr. G. Meyer
Institut fürAno rg anische Chemie
Universität zu Köln
molecule has a volume of 1.48 nm and a diameter of 1.42 nm
(if it were spherical).
The “nanomolecule” Sc C I has an outer envelope of
2
4
10 30
Greinstrasse 6, 50939 Köln (Germany)
Fax: (+49)221-470-5083
E-mail: a.mudring@uni-koeln.de
gerd.meyer@uni-koeln.de
3
0 iodine atoms (Figure 2). A T4 supertetrahedron would
1
consist of 35 iodine atoms (according to ꢀatoms = [ = (n+1)
6
(n+2)(n+3)], for a Tn supertetrahedron, with n = 4), but as it
is hollow (À1 iodine atom) and truncated at the four corners
[
**] This work has been supported by the Deutsche Forschungsge-
meinschaft (SFB 608 “Komplexe Übergangsmetallverbindungen
mit Spin- und Ladungsfreiheitsgraden und Unordnung”) and by the
Alexandervon Humboldt Stiftung (postdoc stipend to L.J.).
(
À4 iodine atoms), there are only 30 iodine atoms in the outer
shell. This truncated, hollow T4* supertetrahedron surrounds
a T3 supertetrahedron of 20 scandium atoms, which is filled
1
886
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2006, 45, 1886 –1889

Angewandte
Chemie
[
9]
nitrogen. Pairs of Sc C I molecules are oriented with
2
4
10 30
their triangular faces towards each other; the distance
between the centers of the molecules is 1190 pm (Figure 4).
Figure 2. Space-filling model of the Sc C I molecule. Sc blue,
2
4 10 30
C black, I pink.
by a T2 supertetrahedron of 10 carbon atoms, which, in turn,
is filled by a T1 tetrahedron of four scandium atoms
(
Figure 3). Therefore, the molecular structure of Sc C I ,
24 10 30
which can be described as Sc C Sc I = T1 + T2 + T3 + T4*,
4
10
20 30
is reminiscent of a Russian doll, or, in other words, the
molecule has an onion-like structure.
Figure 4. Spatial arrangement of the inner Sc T1 tetrahedra, which are
4
representative of the complete Sc C I molecules, as viewed down
2
4 10 30
In the Sc C I molecule, the 20 scandium atoms of the
the [111] direction. The similarity between the structures of Sc C I
2
4
10 30
24 10 30
T3 supertetrahedron form 10 tetrahedra, which share
common vertices and are filled with single carbon atoms.
Each of the octahedral interstices of the T3 supertetrahedron
and solid nitrogen is highlighted by the dashed lines, which indicate
pairs of molecules, as described in the text.
Of course, unlike the nitrogen
atoms in the N molecules, the
2
Sc C I molecules are only
2
4
10 30
held together by van der Waals
interactions.
The Sc20 T3 supertetrahe-
3
0+
dron of the {Sc C Sc }
ion
4
10
20
3
0À
in its {I }
envelope has the
3
0
same structure as the recently
discovered Au supertetrahe-
2
0
[
10]
dron. A filled supertetrahe-
dral anion was also found in
Cs [Sn O S ](H O) ,
for
8
10
4
11]
20
2
13
Figure 3. Structure of the Sc C I molecule: Sc =T1; Sc C =T1+T2; Sc C Sc =T1+T2+T3;
2
4
10 30
*
4
4
10
4
10
20
[
*
example.
Supertetrahedra
Sc C Sc I =T1+T2+T3+T4 (T4 is the truncated, hollow T4 supertetrahedron). Sc blue, C black,
4
10
20 30
I pink.
are by no means uncommon in
[
12]
chalcogenide
chemistry,
although the first oxidic T5
is occupied by one of the vertices of the inner Sc4 T1
tetrahedron. The 10 carbon atoms have the same arrange-
ment as the carbon atoms in adamantane (C H ); both
supertetrahedron was only recently observed in
[
13]
Na Mn O .
2
6
39 55
4
À
1À
In Sc C I (with C and I ), scandium has an oxidation
1
0
16
24 10 30
structures can be interpreted as fragments of the diamond
lattice. They also have the same topology as the oxygen atoms
in P O , which encapsulate a P tetrahedron. Thus, the P O
state of slightly less than + 3 (+ 2.92), if a purely ionic model
is considered. Hence, there are two excess electrons per
3
+
4À
À
À
2
molecule, according to (Sc ) (C ) (I ) (e ) . These elec-
4
10
4
4
10
24
10
30
molecule and the Sc C10 fragment are isostructural. The
trons can be expected to reside in the empty Sc tetrahedron,
4
4
shortest ScÀSc distance in Sc C I is only 276 pm, much
in analogy to the 20 electrons that occupy 10 bonding orbitals
2
4
10 30
shorter than that in Sc C I (302 pm). Additionally, the ScÀC
(four-center, two-electron (4c–2e) bonds) in the naked Au
4
2
6
20
[
10]
interactions of 200–210 pm in the Sc C tetrahedra of Sc C I
cluster.
Indeed, extended Hückel molecular orbital
4
24 10 30
1
0+
must be regarded as strong, when compared with the ScÀC
(EHMO) calculations for {Sc4}
,
as well as for
3
0+
[14]
distances of approximately 230 pm observed in the Sc C
{Sc C Sc }
reveal similar bonding pictures.
In both
6
4
10
20
[
8]
octahedra of Sc{Sc C}I .
cases, the HOMO is a 4c–2e orbital (Figure 5). Of course, the
6
12
¯
In the cubic unit cell (Pa3), the Sc C I molecules are
empty Sc tetrahedron could also be filled with two hydrogen
2
4
10 30
4
arranged in the same way as the nitrogen atoms in solid
atoms, which would consume the two electrons. Although the
Angew. Chem. Int. Ed. 2006, 45, 1886 –1889
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
1887

Communications
[
2] G. Meyer, L. Jongen, A.-V. Mudring, A. Möller, Inorg. Chem.
Focus 2005, 2, 105.
[
3] A. Lachgar, D. S. Dudis, P. K. Dorhout, J. D. Corbett, Inorg.
Chem. 1991, 30, 3321.
[
[
[
4] G. Meyer, J. D. Corbett, Inorg. Chem. 1981, 20, 2627.
5] D. S. Dudis, J. D. Corbett, Inorg. Chem. 1987, 26, 1933.
6] Synthesis: Sc2.4CI =^ Sc C I was obtained as a by-product in
3
24 10 30
an attempt to synthesize Sc C I , starting from ScI , scandium,
6
2
11
3
and graphite (molar ratio 1:1:1). ScI was synthesized from the
3
elements and sublimed under high vacuum at 1193 K. Scandium-
metal pieces and graphite were used as purchased. All starting
materials and products were stored and manipulated in an
argon-filled glove box (MBraun, Garching). The reaction was
carried out in a sealed tantalum container, jacketed with a fused-
silica tube, at a temperature of 1123 K. After two weeks, the
reaction mixture was cooled by turning off the power to the
furnace. Good quality blue-black single crystals of Sc C I
1
0+
Figure 5. The HOMOs forthe {Sc } tetrahedron (left) and the
4
3
0+
{
Sc C Sc } cluster (right), as well as the molecular orbital diagram
4 10 20
for{Sc C Sc } , obtained from EHMO calculations.
3
0+
4
10
20
hydrogen atoms in related compounds usually occupy octa-
hedral sites, which are displaced away from the center
towards a triangular face of the octahedron, the possibility
2
4
10 30
were obtained, along with a black powder and single crystals
of Sc C I . X-ray powder diffraction at room temperature
that hydrogen atoms occupy the Sc tetrahedron cannot be
6
2 11
4
(
(
transmission mode, Imaging Plate Guinier Camera G670
Huber, Rimsting)), monochromatic MoKa radiation) revealed
completely ruled out. However, the yield was not enhanced
when hydrogen was deliberately added to the reaction, either
as ScH2 or as hydrogen gas, which diffuses through the
tantalum container at the chosen reaction temperature.
In the Sc/C/I system (Figure 1), Sc CI = (Sc ){(Sc ) -
C )(e ) }(I ) , in which single carbon atoms occupy the
5
centers of scandium octahedra, is certainly the most stable
compound. In Sc C I and Sc C I , C (ethanide) units
occupy the scandium octahedra. In Sc C I , the octahedra
share trans edges to form chains. Every second octahedron is
distorted in such a way that it can also be described as two
tetrahedra sharing a common edge. As mentioned above,
Sc C I is only slightly more reduced than Sc C I =^
Sc C I . Thus, it can be argued that the incorporation of
an empty Sc tetrahedron stabilizes the Sc C I oligomer.
that the product mainly consists of two phases, Sc C I and
6
2 11
Sc C I . Sc C I could not be detected by X-ray powder
4
2
6
24 10 30
diffraction at room temperature.
3
+
3+
7
12
6
[7] Crystal data and structure refinement: A suitable single crystal
(0.3 ” 0.2 ” 0.2 mm) was sealed in a glass capillary in an argon-
filled glove box. Intensity data were collected at room temper-
ature on an IPDS I diffractometer, and at 130 K on an IPDS II
4
À
À
À
(
12
[
8]
6
2
11
4
5]
2
6
2
¯
[
diffractometer (both Stoe, Darmstadt). 130(2) K: cubic, Pa3
4
2
6
3
(
4
No. 205); a = 2551.82(5) pm, V= 16.6169(6) nm ; Z = 8, 1
=
calcd
À3
.002 gcm ; 1.38 < q/8 < 24.99; Mo radiation (l = 71.073 pm);
F(000) = 17232; m = 12.973 mm ; 139853 reflections measured,
Ka
À1
4879 unique, 3997 observed; R1 = 0.0281, wR2 = 0.0654 (for I >
o
¯
2s(I
1
)). 293 K: cubic, Pa3 (No. 205); a = 2568.4(3) pm, V=
2
4
10 30
4
2 6
o
3
À3
6.943(3) nm ; Z = 8, 1calcd = 3.925 gcm ; 2.24 < q/8 < 23.85;
2
0
10 30
MoKa radiation (l = 71.073 pm); F(000) = 17232; m =
4
24 10 30
À1
1
2.723 mm ; 51375 reflections measured, 4346 unique, 2331
Oligomers are rather uncommon in the chemistry of intersti-
tially stabilized rare-earth-metal halide clusters. With scan-
observed; R1 = 0.0668, wR2 = 0.1378 (for I > 2s(I )). The data
o
o
were processed with the program SHELX-97 [G. M. Sheldrick,
SHELX-97, Universität Göttingen, 1997]. Scattering factors
were taken from: A. J. C. Wilson, International Tables for
Crystallography, Vol. C, Mathematical, Physical and Chemical
Tables, Kluwer, Dordrecht, The Netherlands, 1995. Numerical
absorption corrections were performed after crystal-shape
optimization using the programs XRED and XSHAPE [Stoe,
XRED 1.01 and XSHAPE 1.01, Darmstadt, 1996]. Further
details on the crystal structure investigations may be obtained
from the Fachinformationszentrum Karlsruhe, 76344 Eggen-
stein-Leopoldshafen, Germany (fax: (+ 49)7247-808-666;
e-mail: crysdata@fizkarlsruhe.de), on quoting the depository
numbers CSD-414259(130 K) and CSD-414260 (2 93 K).
dium, the bromides Sc Z Br (Z = Mn, Fe, Ru, Os) are
1
9
4
28
[
15]
known. These compounds contain the R Z X oligomer
1
6
4
20
(
R = rare-earth metal, X = halogen) first observed for
[
16]
Y RuI .
The component R Z4 cluster consists of four
16
4
5
edge-sharing R Z octahedra. Carbon atoms in tetrahedral
6
[
17]
interstices are known from RbPr C Cl . In this compound,
5
2
10
two Pr C tetrahedra share a common face to form a Pr5
4
trigonal bipyramid, which encapsulates a C unit.
2
The crystal structure of Sc C I consists of molecules of
2
4
10 30
the same composition, which are packed in the same way as
the nitrogen atoms in solid nitrogen. The molecules have an
À
[8] D. S. Dudis, J. D. Corbett, S.-J. Hwu, Inorg. Chem. 1986, 25, 3434.
onion- or Russian-doll-like structure, (e ) Sc C Sc I , and
2
4
10
20 30
[
9] a) J. Donohue, Acta Crystallogr. 1961, 17, 1000; b) J.A. Venables,
C. A. English, Acta Crystallogr. Sect. B 1974, 30, 929; and
references therein.
contain two excess electrons, which reside in the inner Sc4
tetrahedron and occupy a 4c–2e orbital.
[
10] a) J. Li, H.-J. Zhai, L.-S. Wang, Science 2003, 299, 864; b) R. B.
King, Z. Chen, P. von R. Schleyer, Inorg. Chem. 2004, 43, 4564.
11] W. Schiwy, B. Krebs, Angew. Chem. 1975, 87, 451; Angew. Chem.
Int. Ed. Engl. 1975, 14, 436.
Received: November 4, 2005
Published online: February 17, 2006
[
Keywords: carbon · electronic structure · iodine · scandium ·
supertetrahedra
[12] a) H. Li, M. OꢀKeeffe, O. M. Yaghi, Science 1999, 283, 1145;
b) B. Feng, X. Bu, N. Zheng, Chem. Eur. J. 2004, 10, 3356.
.
[
13] A. Möller, P. Amann, V. Kataev, N. Schittner, Z. Anorg. Allg.
Chem. 2004, 630, 890.
[
14] Theoretical calculations: Semi-empirical EHMO calculations
1
0+
30+
[
1] a) B. C. McCollum, J. D. Corbett, Chem. Commun. 1968, 1666;
b) B. C. McCollum, D. S. Dudis, A. Lachgar, J. D. Corbett, Inorg.
Chem. 1990, 29, 2030.
for the molecular clusters {Sc
4
}
and {Sc
C
4
10Sc20
}
were
performed with the program package CAESAR [J. Ren, W.
Liang, M.-H. Whangbo, CAESAR, PrimeColor Software Inc.,
1
888
www.angewandte.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2006, 45, 1886 –1889

Angewandte
Chemie
Raleigh, NC, USA, 1998.] with the following parameters
double-zeta functions): H [eV], z , coefficient 1, z , coeffi-
(
ij
1
2
cient 2: Sc: 4s À7.05, 1.5, 0.5172, 0.9, 0.587; 4p À3.98, 1.14, 1.0,
0
1
.0, 0.0; 3d À8.35, 4.4, 0.359, 2.0, 0.766; C: 2s À19.66, 1.98, 0.7931,
.24, 0.2739; 2p À10.86, 2.2, 0.2595, 0.96, 0.8026.
[
[
[
15] S. J. Steinwand, J. D. Corbett, J. D. Martin, Inorg. Chem. 1997,
3
6, 6413.
16] M. W. Payne, M. Ebihara, J. D. Corbett, Angew. Chem. 1991,
03, 842; Angew. Chem. Int. Ed. Engl. 1991, 30, 856.
1
17] G. Meyer, S. Uhrlandt, Angew. Chem. 1993, 105, 1379; Angew.
Chem. Int. Ed. Engl. 1993, 32, 1318.
Angew. Chem. Int. Ed. 2006, 45, 1886 –1889
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
1889