Preparation of decachlorocorannulene and other perchlorinated fragments of fullerenes by electrical discharge in liquid chloroform

Article abstract of DOI:10.1021/ja970238w

The discharge reaction of decachlorocorannulene and other perchlorinated fragments of fullerenes is studied in liquid chloroform using electrical discharge. Results reveal various reaction products. It is shown that all the characterized products are perchlorinated fragments of C₆₀.

Full text of DOI:10.1021/ja970238w

5954
J. Am. Chem. Soc. 1997, 119, 5954-5955
Communications to the Editor
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Preparation of Decachlorocorannulene and Other
Perchlorinated Fragments of Fullerenes by
Electrical Discharge in Liquid Chloroform
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Rongbin Huang, Weijie Huang, Yuhuang Wang,
Zichao Tang, and Lansun Zheng*
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State Key Laboratory for Physical
Chemistry of Solid Surface, Department of Chemistry
Xiamen UniVersity, Xiamen, Fujian, China 361005
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ReceiVed January 27, 1997
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Since the pioneering work of Kratscher and Huffman,1 C60
and other fullerenes have been prepared by arc discharge
between graphite electrodes in helium atmosphere. Grosser and
Hirsch2 vaporized graphite under similar conditions but in the
presence of (CN)2 and obtained a series of dicyanopolyyne
products. When experiments were carried out in Cl2 atmo-
sphere, hexachlorobenzene and other perchlorinated compounds
appeared as the main products.2 Recently, we have performed
the arc discharge experiments in a different way where the
discharge reaction is allowed to proceed in liquid rather than
in the gas atmosphere. In this paper, we report the discharge
reaction performed in liquid chloroform. Various reaction
products have been obtained, from which decachlorocorannulene
and some other perchlorinated aromatic compounds have been
separated and characterized. The results in this work are of
significance in understanding the formation mechanism of
fullerenes, as it will be shown that all of the characterized
products are perchlorinated fragments of C60.
The experiment was performed in a 500-mL three-necked
flask. The reagent is 300 mL of chloroform which was purified
before the reaction to eliminate the possible contamination
(including aromatic compounds). Purity of the reagent was
examined by GC-MS analysis. During the reaction, purified
nitrogen gas was bubbled through the reagent to preserve an
inert atmosphere. Two copper electrodes, mounted on the each
of the two side necks of the flask, were immersed into the liquid
at a fixed angle. The gap between the two electrodes was about
1 mm. An ac voltage over 10 kV in 20 kHz was applied to the
electrodes. The stable arc discharge could be maintained by
adjusting either the applied voltage or the gap distance between
the electrodes. The arc current of 20-50 mA was typical in
the present work. A large amount of acidic gases were produced
during the reaction which was characterized as the mixture of
HCl and Cl2. A deep red-brown solution was obtained after a
5-h discharge. After the remaining solvent was removed by
vacuum evaporation, 3-4 g of residue was collected. About
40% of the residue was sublimated at 160 °C as colorless needle
crystals (I). The remainder was dissolved in benzene and
separated by neutral Al2O3 column chromatography, with
petroleum ether / benzene in different ratios as the elute. Several
fractions have been collected with different yields: 8% light
yellow needle crystal (II), 20% orange needle crystal (III), 12%
green feather crystals (IV), and 8% brown powder (V).
Separation and characterization of other products, which amount
to more than 10% of the residue, are still in progress.
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(IV)
(V)
consist of chlorine and carbon only. The reacted solution was
analyzed by GC-MS before the column chromatographic
separation, and various products with low boiling points, such
as C2Cl4, C3Cl6, C4Cl8, C4Cl6, and C5Cl6, were detected.
Chemical formulas of the separated products I-V were
determined by mass spectrometry. From the masses and the
isotopic patterns of molecular ion peaks in the recorded mass
spectra,3 the products can be assigned to C6Cl6 (I), C10Cl8 (II),
C12Cl8 (III), C16Cl10 (IV), and C20Cl10 (V), respectively. When
the IR and UV-vis data of the products4 were compared with
those of known compounds, products I-IV could be further
identified as hexachlorobenzene (I), octachloronaphthalene
(II),5,6 octachloroacenaphthylene (III),7 and decachlorofluoran-
thene (IV),8,9 respectively. In addition, XRD results of product
I are consistent with that of the known hexachlorobenzene
compound.
Although the molecular formula C20Cl10 may correspond to
a few structural isomers, the decachlorocorannulene seems to
be most likely. Scott reported the preparation of this compound,
but no spectral data are available.10 Further investigation using
13C- and 35Cl-NMR spectroscopy was, therefore, carried out in
the present work in addition to the IR and UV-vis measure-
ments.11 There are three peaks in the recorded 13C-NMR
(3) Mass peaks of the molecular ions in m/z (%): product I 282 (51.43),
284 (100.00), 286 (76.58), 288 (33.14), 300 (6.29); product II 400 (32.14),
402 (85.71), 404 (100.00), 406 (64.29), 408 (28.57); product III 432 (4.14),
430 (23.99), 428 (62.00), 426 (100.00), 424 (80.12), 422 (27.76); product
IV 554 (4.80), 552 (20.38), 550 (50.66), 548 (98.67), 546 (100.00), 544
(66.58), 542 (19.09); product V 590 (20.50), 592 (66.67), 594 (100.00),
596 (88.89), 598 (51.85), 600 (20.74), 602 (17.28).
(4) Spectroscopic data: product I UV-vis/CCl4 λmax ) 272 nm, IR 1340
(s), 1295 (m), 715 (w), 690(s); product II UV-vis/C2H5OH λmax ) 270
nm, IR 1730 (w), 1520 (s), 1414 (m), 1355 (w), 1290 (s), 1270 (s), 1250
(s), 1220 (w), 1165 (m), 1060 (w), 965 (m), 860 (w), 780 (w), 750 (w),
690 (m), 665 (m); product III UV-vis/C6H12 λmax ) 365 nm, IR 1555
(m), 1495 (m), 1415 (m), 1365 (m), 1290 (m), 1230 (m), 1160 (m), 1120
(s), 700 (m); product IV UV-vis/C6H6 λmax ) 220 nm, IR 1525 (w), 1370
(s), 1350 (m), 1330 (m), 1300 (s), 1265 (m), 1150 (s), 1030 (m), 915 (m),
895 (m), 805 (m), 690 (m).
(5) . Kalmykova, G. O.; Kurmei, N. D.; Malykhina, N. N. IzV. Akad.
Nauk SSSR, Ser. Fiz. (Russ.) 1975, 39 (9), 1925-1929.
(6) Atlas of Spectral Data and Physical Constants for Organic Com-
pounds, 2nd ed. Grasselliet, J. G., Ritchey, W. M., Ed.; CRC Press:
Cleveland, OH, 1975; Vol. 3, pp 645-646.
(7) Mack, W. Tetrahedron Lett. 1966, 25, 2875.
Characterization of the above obtained species were carried
out at different stages. None of the signals that appeared in
the 1H-NMR spectra can be assigned to any of the characterized
products. It can, therefore, be concluded that the products
(8) Lifshitz, C.; Peres, T.; Agranat, I. Int. J. Mass Spectrom. Ion Processes
1989, 93, 154.
(9) Ballester, M.; Castaner, J.; Riera, J.; Pares, J. An. Quim. 1980, 76,
168.
(10) Scott, L. T. Pure Appl. Chem. 1996, 68, 293.
(1) Kratschmer, W.; Lamb, L. D.; Fostiropoulos, K.; Huffman D. R.
Nature 1990, 347, 354.
(2) Grosser, T.; Hirsch A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1340.
(11) Spectroscopic data of product V: UV-vis/C6H5CH3 λmax ) 290
nm; IR 1720 (m), 1540 (m), 1455 (s), 1360 (s), 1340 (m), 1290 (m), 1270
(m), 1250 (m), 1150 (m), 1090 (m), 1010 (w), 950 (s), 710 (m).
S0002-7863(97)00238-2 CCC: $14.00 © 1997 American Chemical Society

Communications to the Editor
J. Am. Chem. Soc., Vol. 119, No. 25, 1997 5955
spectra, 129.62, 128.37, and 128.16 ppm, with a ratio of 2:1:1
and a single peak in 35Cl-NMR, 507.36 ppm, which is consistent
with the structure of decachlorocorannulene.
frameworks kept unchanged. Another interesting structural
feature is that rings of the product compounds tend to pack
together rather than forming a relatively simple polycyclic
structure like that in anthracene. In particular, the occurrence
of five-membered-ring is noteworthy as it is essential for the
formation of C60 and other fullerenes. In fact, all of the
characterized products in the present work can be considered
as the perchlorinated intermediates in forming C60. Therefore,
the significance of the reaction is not limited to the synthesis
of the decachlorocorannulene and other perchlorinated products;
it is also helpful to the understanding of the formation
mechanism of fullerenes.
Although the reagent of the experiment, chloroform mol-
ecules, contain a single carbon atom only, in the discharging
reaction, they serve as C1 building block, which aggregate to
structures that are parts of the fullerene framework. Hence, the
extension of the discharging reaction from the gas phase into
the liquid media allows the synthesis of interesting and novel
compounds. The experimental results reported in this paper
has demonstrated the potential ability of the technique.
The discharging reaction in liquid was expected to be
complex. Surprisingly, however, the experimental results of
the present work show that the reaction products are quite
selective: All of the products that have been characterized so
far are perchlorinated polycyclic compounds. In fact, we have
also performed a similar experiment in CCl4, and the same
products were obtained. Among various possibilities is that
dichlorocarbene is the reaction intermediate which aggregates
to form the observed products. Other radical pathways may
also be envisioned. When the formation enthalpies of :CCl2
and :CHCl are compared with that of CHCl3,12 it can be shown
that formation of the former is thermodynamically favorable.
Therefore, hydrogen can be ruled out in composition from all
of the products.
It is clear from the structural analysis that all of the
characterized products of the discharging reaction are aromatic
compounds. Their structural stability is also demonstrated by
the EI mass spectra showing predominant signal intensity of
the molecular ions. Under electron bombardment, these mo-
lecular ions lose chlorine atoms one by one with carbon
Acknowledgment. This work was supported by the National Natural
Science Foundation of China and the State Educational Commission
of China.
(12) CRC Handbook of Chemistry and Physics, 51st ed.; Weast, R. C.,
Ed.; CRC Press: Cleveland, OH, 1970; pp D64-D72.
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