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Synthesis and Structure of the Highly Chlorinated [60]Fullerene C60Cl30 with a Drum-Shaped Carbon Cage.

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Angewandte
Chemie
Communications
The highly chlorinated, thermally stable [60]fullerene
C60Cl30 contains a cylinder-shaped carbon cage consisting of two
aromatic six-membered rings and one equatorial 18p-trannulene belt
separated by two 15-membered belts of sp3 carbon atoms bearing Cl
substituents. Find out more about the synthesis and properties of
C60Cl30 in the Communication by P. A. Troshin, S. I. Troyanov et al. on
the following pages.
234
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/anie.200461531
Angew. Chem. Int. Ed. 2005, 44, 234 ? 237
Angewandte
Chemie
Fullerenes
Synthesis and Structure of the Highly Chlorinated
[60]Fullerene C60Cl30 with a Drum-Shaped
Carbon Cage**
Pavel A. Troshin,* Rimma N. Lyubovskaya,
Ilya N. Ioffe, Natalia B. Shustova, Erhard Kemnitz, and
Sergey I. Troyanov*
Halogenated fullerenes are versatile precursors for the synthesis of various complex derivatives, some of which exhibit
promising properties for material science applications.[1] To
date, considerable success has been achieved in preparation
and structural characterization of fullerene bromides[2] and
fluorides.[3] Despite numerous reports on chlorination of C60
by different reagents,[4] only two individual compounds have
been isolated so far. The structure of C60Cl6 formed in the
reaction of ICl with C60 in benzene was deduced from the
13
C NMR and IR spectra.[4b] C60Cl24 was synthesized using
VCl4 and SbCl5 ; a tetrahedral structure similar to that of
C60Br24[2a, d] was assigned to this chloride on the basis of a
comparison between the experimental and theoretically
calculated IR spectra.[5]
Here we report the synthesis and structural characterization of the novel, highly chlorinated fullerene C60Cl30. This
chlorofullerene can be prepared using chlorinating agents
such as ICl, ICl3, and SbCl5. Typically, 50?100 mg of C60 and a
large excess (~ 2 g) of chlorinating agents were sealed in glass
ampules and heated at 220?250 8C for one to three days. Then,
the ampules were opened, and the excess of the chlorinating
agents and their decomposition products were removed in
vacuo at 150 8C. Pure C60Cl30 (1) was formed in the reaction of
C60 with SbCl5, whereas chlorination by ICl yielded the
C60Cl30�ICl solvate (2), both as dark-orange crystals stable in
air. The IR spectrum of C60Cl30 is presented in Figure 1. The
most prominent bands are observed at n? = 439, 450, 471, 479,
730, 775, 822, 854, 895, 903, 918, 958, 993, and 1447 cm 1.[6]
Figure 1. The experimental (top) and calculated (bottom) IR spectra of
C60Cl30.
C60Cl30 is insoluble in most common organic solvents such as
diethyl ether, 1,4-dioxane, CH2Cl2, CHCl3, and CCl4 ; it is
poorly soluble in CS2, toluene, and chlorobenzene; and its
solubility in 1,2-dichlobenzene was estimated at roughly
0.2 mg mL 1. The thermal stability of C60Cl30 appears to be
remarkably high: its decomposes into C60 and Cl2 at 450?
500 8C (Figure 2), which is about 120 8C higher than the
temperature ranges previously reported for C60Cl24.[4b, 5] The
mass loss for C60Cl30, 60.1 %, corresponds well to the
calculated value of 59.75 %.
[*] P. A. Troshin, Prof. R. N. Lyubovskaya
Institute of Problems of Chemical Physics of RAS
142432 Chernogolovka, Moscow Region (Russia)
Fax: (+ 7) 096-2521852
E-mail: troshin@cat.icp.ac.ru
Dr. I. N. Ioffe, N. B. Shustova, Prof. Dr. S. I. Troyanov
Chemistry Department
Moscow State University
119992 Moscow (Russia)
Fax: (+ 7) 095-9391240
E-mail: troyanov@thermo.chem.msu.ru
Prof. Dr. E. Kemnitz
Institut fr Chemie
Humboldt-Universitt zu Berlin
12489 Berlin (Germany)
[**] This work was supported in part by the Deutsche Forschungsgemeinschaft (KE 489/20-1) and by the Russian Foundation for Basic
Research (03-03-04006 and 04-03-32870a). We are grateful to A. A.
Popov for his help in scaling the calculated IR spectrum, and to M.
Feist and N. V. Chelovskaya for thermoanalytical measurements.
Angew. Chem. Int. Ed. 2005, 44, 234 ?237
Figure 2. Thermoanalytical data for C60Cl30�ICl (a) and C60Cl30 (b).
www.angewandte.org
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
235
Communications
X-ray single-crystal structures of both C60Cl30 (1) and
C60Cl30�ICl (2) were determined with good accuracy.[7] While
the isolated molecule of C60Cl30 should possess D3d symmetry,
crystallographically imposed symmetry in 1 and 2 becomes
reduced to Ci and C2h, respectively. There are two planar
aromatic six-membered rings on the opposite sides of the cage
and an equatorial 18p all-trans annulene (trannulene) belt in
the chlorofullerene molecule (Figure 3). C60Cl30 is the first
molecule in which the trannulene belt is separated from the
benzenoid rings by two 15-membered rings of sp3 carbons
bearing chlorine atoms. Such a structural arrangement results
in the unique cylindrical, drumlike shape of the carbon cage.
The fluorofullerene molecule C60F18 contains one sixmembered planar aromatic fragment which is surrounded by
the fluorinated belt of 15 sp3 carbons.[8] The SN2? substitution
of three additional outlying fluorine atoms by various
malonate groups yields compounds having the composition
C60F15[CX(COOR)2]3, which also contain [18]annulene belts.
These subunits satisfy the magnetic and geometric criteria of
aromaticity, even though they are not completely isolated
from the rest of the p system.[1, 9]
The IR spectroscopic and mass spectrometric study of the
products collected before the completion of the reaction
revealed that tetrahedral C60Cl24 is an intermediate in the
synthesis of C60Cl30. Noteworthy, the formation of D3d C60Cl30
from Th C60Cl24 requires rearrangement of at least 18 Cl atoms
over the fullerene cage. The analogous migration of fluorine
atoms yielding the most thermodynamically stable structures
is called the ?fluorine dance? and is known for the fluorination of C60F36 to give C60F48[10a] and for the transformation of
C1 C60F36 into C3 C60F36 by fluorine rearrangement.[10b] The
formation of C60Cl30 from C60Cl24 is the first observation of the
?chlorine dance?. The thermally induced ?chlorine dance?
appears to be slow enough for other possible intermediates to
be isolated by termination of the reaction at a certain stage.
Quantum chemical calculations at the DFT level of theory
were performed to examine the relative stability of various
higher chlorides of C60.[11] Two main factors were found to
influence the stability of chlorofullerenes beyond C60Cl24 :
destabilizing van der Waals repulsions between the adjacent
chlorine atoms and the stabilizing effect of the aromatic
fragments such as benzenoid rings. Particularly high steric
strain was observed for the structures containing chlorine
atoms surrounded by three others (?triple contacts?). Ruling
out the ?triple contacts? results in a maximum of two isolated
benzenoid rings in the closed-shell chlorofullerene molecules.
One of two possible structures containing two aromatic sixmembered rings and no ?triple contacts? corresponds exactly
to the presently found isomer of C60Cl30. It is approximately
110 kJ mol 1 more stable than the second possible C60Cl30
isomer, which is characterized by nonparallel arrangement
of two aromatic six-membered rings. The remarkable thermal
stability of C60Cl30 might have a kinetic origin since detachment of any chlorine atom would perturb the stable aromatic
fragments. C60Cl30 probably represents the terminal stage of
C60 chlorination since further chlorine attachment would
involve a strongly unfavorable destruction of the aromatic
rings.
The averaged experimental and calculated molecular
structures of C60Cl30 are in very good agreement (Table 1).
The aromatic six-membered rings are almost perfectly planar;
the sum of the valence angles involving aromatic carbons
exceeds 359.98; and the 6/6 (a?) and 5/6 (a??) C C bonds in
these rings are virtually equal. Similar equalization of the 6/6
(h) and 5/6 (i) bonds is seen in the equatorial trannulene ring,
which serves as additional evidence of its aromatic character.
The sp3?sp3 C C bonds appear to be strongly elongated,
reaching a value of 1.70 (e). For comparison, similar bonds
in C60F18 and C60F36 are ?only? 1.67 long.[9, 12] The calculated
IR spectrum of C60Cl30 is in a good agreement with the
experimental one (Figure 1).
It is known that oxygen can attack the elongated C C
bonds in C60F18, which results in their cleavage and formation
of intramolecular ethers.[13] Impurities of C60F18O in some
C60F18 samples have been observed by means of X-ray singlecrystal diffraction.[9b] In these cases, the presence of oxygen
was manifested in the characteristic maxima near the
elongated C C bonds on electron density maps. Similar
peaks were found for 1 a (synthesized with nonpurified
SbCl5),[7] where one of the e bonds was elongated up to
Figure 3. The top and side views and the Schlegel diagram of the C60Cl30 molecule.
236
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2005, 44, 234 ?237
Angewandte
Chemie
Table 1: C C and C Cl bonds [] in C60Cl30 according to the averaged
data[a] for structures 1 and 2 and DFT calculations.
Bond type[b]
1
2
Calcd
C C
a?, sp2 sp2, 6/6
a??, sp2 sp2, 5/6
b, sp2 sp3, 5/6
c, sp3 sp3, 6/6
d, sp3 sp3, 5/6
e, sp3 sp3, 5/6
f, sp2 sp3, 5/6
g, sp2 sp3, 6/6
h, sp2 sp2, 6/6
i, sp2 sp3, 5/6
1.367
1.377
1.476
1.576
1.622
1.693
1.509
1.494
1.381
1.391
1.372
1.374
1.476
1.582
1.620
1.699
1.509
1.494
1.386
1.392
1.372
1.380
1.479
1.582
1.628
1.699
1.509
1.496
1.381
1.391
C Cl
1
2
3
1.776
1.788
1.787
1.772
1.786
1.779
1.800
1.815
1.811
[5]
[6]
[7]
[a] Estimated standard deviations of individual bond lengths in 1 and 2
are 0.002 and 0.003?0.004 , respectively. [b] Bond labels are defined
in the Schlegel diagram in Figure 3.
1.722 , as compared to 1.690 for the rest two e bonds.
Taking into account a statistical averaging with the parent
C60Cl30, this additional elongation indicates the presence of
the C60Cl30O2 ether (about 7 %) with two cleaved C C bonds.
The chemical properties of C60Cl30 may be rather versatile.
Firstly, the weak elongated C C bonds can be regarded as a
convenient site for further derivatization of this molecule. The
benzenoid moieties can allow organometallic h6-coordination,
as it was previously observed for C60F18.[14] Our preliminary
experiments showed that C60Cl30 can undergo nucleophilic
substitution reactions though significantly slower than C60Cl24.
Detailed investigation of C60Cl30 reactivity is a subject for
further studies.
[8]
[9]
[10]
[11]
Received: August 4, 2004
Published Online: November 12, 2004
.
Keywords: chlorination � density functional calculations �
fullerenes � structure elucidation
[12]
[13]
[14]
[1] G. A. Burley, A. G. Avent, I. V. Goldt, P. B. Hitchcock, H. AlMatar, D. Paolucci, F. Paolucci, P. W. Fowler, A. Soncini, J. M.
Street, R. Taylor, Org. Biomol. Chem. 2004, 2, 319.
[2] a) F. N. Tebbe, R. L. Harlow, D. B. Chase, D. L. Thorn, G. C.
Campbell, J. C. Calabrese, N. Herron, R. J. Young, E. Wasserman, Science 1992, 256, 822; b) P. R. Birkett, P. B. Hitchcock,
H. W. Kroto, R. Taylor, D. R. M. Walton, Nature 1992, 357, 479;
c) P. A. Troshin, D. Kolesnikov, A. V. Burtsev, R. N. Lubovskaya,
N. I. Denisenko, A. A. Popov, S. I. Troyanov, O. V. Boltalina,
Fullerenes Nanotubes Carbon Nanostruct. 2003, 11, 47; d) S. I.
Troyanov, P. A. Troshin, O. V. Boltalina, E. Kemnitz, Fullerenes
Nanotubes Carbon Nanostruct. 2003, 11, 61.
[3] R. Taylor, J. Fluorine Chem. 2004, 125, 359.
[4] a) G. A. Olah, I. Bucsi, C. Lambert, R. Aniszfeld, N. J. Trivedy,
D. K. Sensharma, G. K. S. Prakash, J. Am. Chem. Soc. 1991, 113,
9385; b) P. R. Birkett, A. G. Avent, A. D. Darwish, H. W. Kroto,
R. Taylor, D. R. M. Walton, J. Chem. Soc. Chem. Commun. 1993,
1230; c) D. Heymann, F. Cataldo, R. Fokkens, N. M. M. NibberAngew. Chem. Int. Ed. 2005, 44, 234 ?237
www.angewandte.org
ing, R. Vis, Fullerene Sci. Technol. 1999, 7, 159; d) P. A. Troshin,
O. Popkov, R. N. Lyubovskaya, Fullerenes Nanotubes Carbon
Nanostruct. 2003, 11, 163.
S. I. Troyanov, N. B. Shustova, A. A. Popov, M. Feist, E.
Kemnitz, Zh. Neorg. Khim. 2004, 49, 1413.
IR spectra were recorded for KBr pellets on a NICOLET-200 FT
spectrometer; 128 scans were averaged and the resolution was
0.5 cm 1.
The data for crystals of C60Cl30�09 Cl2 (1) and C60Cl30�ICl (2)
were collected on an IPDS diffractometer (Stoe) at 170 K and
150 K, respectively (graphite-monochromated MoKa radiation,
l = 0.71073 ). 1: monoclinic, P21/n, a = 12.539(1), b =
13.507(1), c = 17.106(2) , b = 99.98(1)8, V = 2853.3(5) 3, Z =
2; 19 414 reflections collected, 6347independent. Structure
solution with SHELXS-97. The final anisotropic LS refinement
(SHELXL-97) with 416 parameters converged to wR2 = 0.054
and R1 = 0.021. In structure 1 a, additional peaks detected after
location of all atoms in C60Cl30 were treated as one O and two Cl
atoms with refined site occupancy 0.067(2). 2: tetragonal, P42/m,
a = 13.492(2), c = 17.027(3) , V = 3099.5(9) 3, Z = 2; 30 901
reflections collected, 3818 independent. Both ICl molecules are
disordered over several positions. Anisotropic LS refinement
with 257 parameters gave the final values of wR2 = 0.098 and
R1 = 0.035. CCDC 246573?246575 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or
from the Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge CB2 1EZ, UK; fax: (+ 44) 1223-336-033; or
deposit@ccdc.cam.ac.uk).
a) I. S. Neretin, K. A. Lyssenko, M. Yu. Antipin, Yu. L. Slovokhotov, O. V. Boltalina, P. A. Troshin, A. Yu. Lukonin, L. N.
Sidorov, R. Taylor, Angew. Chem. 2000, 112, 3411; Angew. Chem.
Int. Ed. 2000, 39, 3273; b) S. I. Troyanov, O. V. Boltalina, I. V.
Kuvytchko, P. A. Troshin, E. Kemnitz, P. B. Hitchcock, R.
Taylor, Fullerene Sci. Technol. 2002, 10, 243.
G. A. Burley, P. W. Fowler, A. Soncini, J. P. B. Sandall, R. Taylor,
Chem. Commun. 2004, 3042.
a) A. A. Gakh, A. A. Tuinman, Tetrahedron Lett. 2001, 42, 7137;
b) A. Avent, R. Taylor, Chem. Commun. 2002, 2726.
DFT calculations were carried out with the use of the Priroda
code (D. N. Laikov, Chem. Phys. Lett. 1997, 281, 151), which
employs fast implementation of the RI technique. PBE
exchange-correlation functional (J. P. Perdew, K. Burke, M.
Ernzerhof, Phys. Rev. Lett. 1996, 77, 3865) and a basis set of
TZ2P quality were used.
P. B. Hitchcock, R. Taylor, Chem. Commun. 2002, 2078.
O. V. Boltalina, B. de La Vaissire, P. W. Fowler, P. B. Hitchcock,
J. P. B. Sandall, P. A. Troshin, R. Taylor, Chem. Commun. 2000,
1325.
M. D. Francis, O. V. Boltalina, J. F. Nixon, R. Taylor, Fullerenes
Nanotubes Carbon Nanostruct. 2003, 11, 115.
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
237
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drum, structure, synthesis, chlorinated, fullerenes, cage, shape, carbon, highly, c60cl30
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