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Optimization of the Production and Separation of Fullerenes.

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[3] J:M. Lehn in Physicul Cheniistr: of Trunsniernbrune /on Molions (Ed.: G .
Spach), Elsevier, Amsterdam, 1983, pp. 181-207; J.-M. Lehn, Angew.
Chern. 1988, 100. 91; Angex. Chem. Inr. Ed. Engl. 1988, 27, 89.
[4] a) I. Tabushi, Y. Kuroda, K. Yokota. fizruhedrun Leu. 1982. 13. 4601;
b) J. H. Fnhrhop, U. Liman, V. Koesling, J. Arn. Chem. Soc. 1988, 110.
6840, and references therein; c) U. F. Kragten. F. M. Roks, R. J. M. Nolte.
J. Chmi. Sot. Chem. Conimun. 1985. 1275; d) J. D. Lear. Z . R. Wassermann, W. F. De Grado. Science 1988, 1177; e) T. M. Fyles. T. D. James.
K. C. Kaye, Cun. J. Chmr. 1989, 68, 976. and references therein; T. M.
Fyles. K. C. Kaye, T. D. James. D. W. M. Smiley. Tefrahedron Lett. 1990,
3 / , 1233, f) C. J. Stankovic, S. H. Heinemann. S. L. Schreiber. J. . h ? i .
Cheni. Soc. 1990, 112, 3702. and references therein; g) A. Nakano. Q. Xie,
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Menger. D. S. Davis, R. A. Persichetti, J. J. Lee. ;bid. 1990. 112, 2451.
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(61 L. Jullien. J.-M. Lehn, Taruhedron Lerf. 1988. 29, 3803; J. Inclusion Phenom. Mol. Recognil. Chem. 1992, 12, 5 5 ; J. Canceill. L. Jullien, L. Lacombe, JLM. Lehn, Helv. Chim. Acru 1992, 75. 791.
[7] M . M. Pike, S . R. Simon, J. A. Balschi. C. Springer. Jr.. Proc. Nurl. Acud.
Sci. U S A 1982, 79. 810.
[8] a) F. G. Riddell. S. Aruniugam, B. G. Cox, J. Chcm. Soc. Chem. Commun.
1987, 1890; F. G . Riddell. S. Arumugam, P. J. Brophy. B. G. Cox,
M. C. H. Payne. T. E. Southon, J. Am. Cheni. SOC.1988. 110, 734. and
references therein; b) D. C. Shungu. R. W. Briggs, .
Mugn. Reson. 1988.
77, 491, and references therein.
191 R. K. Gupta, P. Gupta, J. Mugn. Reson. 1982, 47, 344; S. C. Chu. M. M.
Pike. E. T. Fossel, T. W. Smith, J. A. Balschi, C. S. Springer, Jr., ibid. 1984,
56. 33; M. M. Pike, D. M. Yarmush, J. A. Balschi, R. E. Lenkinski, C.
Springer, Jr., Inorg. Chem. 1983,22, 2388. and references therein; R. Raniasamy, M. C. Espanol, K. M. Long, D. Mota de Freitas. C. F. G. C.
Geraldes, Inorg. Chrm. Aclu 1989. 163. 41.
[lo] W. N. Konings. K. J. Hellingwerf. G. T. Robillard in Mernbrune Truricporr
(Eds.: S . L. Bonting, J. J. H. H. M. de Pont), Elsevier, Amsterdam, 1981, p.
[ I l l L. T. Mimms, G. Zampighi. Y. Nozaki, C. Tanford. J. A. Reynolds, 5 k chemistry 1981. 20. 833.
[12] P. S. Chen, Jr., T. Y Toribara, H. Warner, Arzul. Chern. 1956. 28, 1756;
W. R. Morrisson. Anal. Biocheni. 1964, 7. 218.
Previous procedures" ' ' 31 succeeded in separating
fullerenes only in small amounts (for example, separation of
400 mg e x t r a ~ t [ ' ~ . 'in
~ I 4-6 hours to give 32 mg C6,["]
after 11 hours or 170 mg C,, after 25 hours[131)incompletely
or only in limited amounts on special column materials. Only
Giigel et a1."61 described a procedure for the separation of
reasonable amounts of a fullerene mixture ( 5 g in 24 hours);
however, a baseline separation was not achieved, and large
mixed fractions were obtained.
In our investigations we used a DC furnace["] for the
preparation of fullerene-containing soot. This has the advantage that the cathodes hardly burn down when electrodes of
equal diameter are used (Fig. 1). We observed a strong
Fig. 1. Drawing of the arc furnace (not to scale): a) water-cooled cathode connection, b) insulation, c) inert gas-vacuum vent, d ) water-cooled stamless-steel
container. e) cooling-water supply, f) water-cooled copper plate, g) cathode
0= 6.15mm, h) close arrangement of anodes @ = 6.15 mm.
change in the ratio of C,,/C,, (hitherto 85:15) in favor of
C,, when we used a higher current. With 400 A DC (hitherto
about 100-200 A, AC or DC) we obtained fullerene mixtures containing up to 50% C,, (Fig. 2). Subsequent extrac-
Optimization of the Production and Separation
of Fullerenes**
By Andreus Mittelbach, Wovgang Honle.
Hans Georg von Schnering,* Jiirgen Carlsen, Rolf Juniuk,
and Helmut Quast*
The observed superconductivity of alkali metal compounds like K3(C6,)[I1 prompted our investigations of
fullerenes. Not only had we looked for a new direction in our
search for superconducting materials,[21we also thought that
K3(Cb0)may be described as an analogue of Zintl phases like
Li,B,,, Li,B,, and Li,B,, (electron transfer with structural
F ~ l l e r e n ecan
s ~ ~be~ produced by laser ~ a p o r i z a t i o n , [va~]
porization of graphite in an
by plasma discharge,"] or
in a high-frequency furnace[*] under reduced pressure of an
inert gas. These methods provide soot containing up to 44%
f ~ l l e r e n e s . [ ~The
- mixture usually consists of C,, and C7, in
a ratio of 85 : 15 and a small amount of higher fullerenes.
Isolation and separation of the fullerenes is achieved by extraction of the soot with toluene followed by chromatogrdphy or directly by chromatography of the soot."']
[*] Prof. Dr. H. G. von Schnering. Dip1:Chem. A. Mittelbach. Dr. W. Honle
Max-Planck-lnstitut fur Festkorperforschung
Heisenbergstrasse 1. D-W-7000 Stuttgart 80 (FRG)
Prof. Dr. H. Quast, Dr. J. Carlsen, Dr. R. Janiak
Institut fur Organische Chemie der Universitit
Am Hubland, D-W-8700 Wiirzburg (FRG)
[**I We thank Dr. H. Schmidt (University of Halle) for preliminary work and
Dr. T. P. Martin (Max-Planck-Institut. Stuttgart) for the measurement of
the TOF mass spectrum.
C: VCH Verlugsgesell.~chufim b H , W-6940 Weinheim. 1992
Fig. 2. Time-of-flight mass spectrum (181 of the soot.
The ordinate corresponds to the ion/time channel.
tion with toluene provided C,,/C,, mixtures greatly enriched in C,,,. Unfortunately, details of the events in the
plasma are not known. All hypotheses about the formation
of fullerenes in the arc are based on the premise of the exisWe presume
tence of single carbon atoms as basic
that the use of high current produces larger regions of higher
temperature. The temperature gradient is much steeper than
that formed at lower current, which favors the formation of
The C6,/C,, mixture could be separated by medium-pressure chromatography according to two procedures (A, B),
both of which start with material dried under vacuum at
200 "C until constant weight was achieved. In procedure A
the fullerene mixture was extracted with hexane (vapor extractor, or extraction, from a precolumn under constant
pressure, which was filled with a mixture of silica gel and
fullerenes). This saturated or oversaturated solution was injected directly onto the separation column and eluted with
0570-0833/9211212-16408 3.50+ ,2510
Angew. Chem. Ini. Ed. Engl. 1992, 31, No. 12
hexane. For the separation we used a glass column with a
high number of plates ( N = 14000) and a good symmetry
index (SI < I .05).[201It is possible to run this procedure continuously. For example, injections can be made every
5-10min (Fig. 3), so that six to three 50mL portions of
toluene/acetonitrile (75:25)from a shunt column which was
filled with a mixture of reversed-phase silica gel and fullerenes (12:l). Injections lasting 45 s were made every 1520 min. In this way we separated up to 300 mg of fullerenes
per hour (Fig. 5). In the chromatogram from procedure B
higher fullerenes like C76,C,,, etc. are apparent. They can
be separated after enrichment.
Experimental Procedure
f Iminl
Fig. 3. Typical chromatogram (detection wavelength 300 nm) for the preparative separation on silica gel with hexane. The lines indicate the cut-offpoints for
the fractions A = absorption.
extract can be separated simultaneously. Depending on the
concentration of the extract, up to 400 mg of fullerenes may
be separated per hour (Fig. 4).
C,, enrichment of the fullerene mixture: The arc furnace [17] was furnished
with graphite electrodes 1221and was evacuated ( 2 Pa) and refilled with helium
gas (purity grade 4.6) several times. Then the furnace was filled with helium to
a pressure of 8 x lo3 Pa. After ignition of the arc at lower current the electrodes
were brought into contact. The intensity of current was raised to 400 A at 58 V
(maximum 18 kW). During the vaporization the pressure was as high as
2 x lo4 Pa. From previous experiments with tungsten electrodes, we know that
the temperature at 400 A and 58 V is higher than 3000 K. We estimate that the
temperature here IS roughly 5000 K at the electrode and about 15000 K in the
plasma. With this method 7- 10 g of graphite per hour could be evaporated.
Afterwards the soot wascollected and extracted with toluene for 24 h. Without
further extraction (for example, as described in ref. [5.7]) the total yield of
fullerenes after removal of the solvent in vacuum was 7- 10%.
Procedure A : Chromatography with hexane on silica gel [23]. A glass column
70x 6 cm) was packed with silica gel (LiChroprep Si60 15-25 pm, Merck) as
described in ref. [20]. Solvent hexane, flow 100 mLmin-’ at 1.6 x 10” Pa. The
fullerene mixture was extracted for 45 min with 200 mL of hexane in a vapor
extractor to remove impurities. This extract was discarded. With another portion of 400 mL hexane the fullerene mixture was extracted in the same way for
4-6 h. This extract was injected in portions of 50 mL every 5-10 min onto the
separation column. The pure fullerenes were then eluted with hexane.
Procedure B: Chromatography with toluene/acetonitrile on C18 reversedphase silica gel [23]. A glass column (70 x 6 cm) was packed with CIX reversedphase silica gel (Europrep 60-30 C18 20-45 pm, Knauer). In an adaptation of
ref. [20]. the column was packed by using methanol/water in a ratio of 95:5:
N = 5000, SI 2 1.25. Solvent toluene/xetonitrile (75:25), flow 72 mLmin- at
1.8 x lo6 Pa. The crude fullerene mixture was loosely mixed with reversedphase silica gel in a ratio of 1: 12 and stored in a 25 x 4 cm glass column which
acted as shunt column and was filled with solvent and kept under pressure.
When the solvent flowed through this precolumn for 45 s the extract was injected on the separation column. The pure fullerenes were then eluted with toluene/
acetonitrile (75:25) [24]
Received: July 30. 1992 [Z 5492 IE]
German version: Angew. Chrm. 1992. 104 1681
Fig. 4. Time-of-flight mass spectrum [lX] after the preparative separation on
silica gel with hexane with only two fractions (Fig. 3). The ordinate corresponds
to the ionitime channel.
[l] R. C. Haddon, A. F. Hebard, M. J. Rosseinsky, D. W. Murphy, S. J.
Duclos, K. B. Lyons, B. Miller, J. M. Rosamilia, R. M. Fleming. A. R.
Kortan, S. H. Glarum, A.V. Makhija, A. J. Muller. R. H. Eick, S. M.
Zahurak, R. Tycko, G. Dabbagh, F. A. Thiel, Narure 1991,350.320; A. F.
In procedure B the chromatography was carried out with
toluene/acetonitrile[ztl(75:25) as the eluent and a glass
column packed with C18 reversed-phase silica gel. The
fullerenes were injected by extraction under pressure with
Hehard. M. J. Rosseinsky. R. C. Haddon, D. W. Murphy, S. H. Glarum.
T. T. M. Palstra, A. P. Ramirez. A. R . Kortan, ibid. 1991, 350. 600.
H. G. von Schnering, L. Walz. M. Schwarz, W. Becker, M. Hartweg, T.
Popp. B. Hettich, P. Miiller, G. Kimpf, A n g w . Chem. 1988, 100. 604;
Anger. Chem. I n t . Ed. Engl. 1988, 27, 574.
H. G. von Schnering, E d . Soc. Chi/.Quim. 1988.33.41 ; G. Mair, Doctoral
Thesis, University of Stuttgart (FRG), 1984; G. Mair, R. Nesper, H. G.
von Schnering in Juhresbericht des Max-Plunck-Instiruts f i r Fe,rkorpcrforschung Slultgurt, Stuttgart 1984.
For a review see, for example: Fullerenes: synthesis, properties, and chemistry ?//urge curbon clusters (Eds.: G. S. Hammond, V. J. Kuck), American
Chemical Society, Washington, DC, 1992. A series of articles appears in
Arc. Chem. Res. 1992, 25. 98-175.
H. W Kroto, J. R. Heath, S. C. OBrien, R. F. Curl. R. E. Smalley, Nuture
1985, 318. 162.
W. Krltschmer. L. D. Lamb. K. Fostiropoulos, D. R. Huffman, Nuture
1991,347, 354.
171 D. H. Parker, P. Wurz. K. Chatterjee, K. R. Lykke, J. E. Hurst. M. J.
Pellin, J. C. Hemminger, D. M. Gruen, L. M. Stock, J. Am. Chem. So<.
1991, 113, 1499.
[S] M. Jansen, G. Peters, Anger.. Chem. 1992,104,240; Angew. Chem. fnr. Ed.
Engl. 1992, 31, 223.
191 8 %: R. Taylor. J. P. Hare, A. Abdul-Sada, H. Kroto, J. Chem. Soc. Chem.
Commim. 1990,1423; 10%: R. E. Haufler, J. Conceicao, L. P. F. Chibante,
Fig. 5. Typical chromatogram (detection wavelength 300 nm) for the preparative separation on C1X reversed-phase silica gel with toluenejacetonitrile
(75:25). A =absorption.
An,qriv. Chrnr. lnt. Ed. Engl. 1992, 31, No. I2
Y Chai, N. E. Byrne, S. Flanagan, M. M. Haley, S. C. O’Brien, C. Pan. Z.
Xiao. W. E. Billups, R. E. Ciufolini, R. N. Hauge, J. L. Margrave, L. J.
Wilson, R. F. Curl, R. E. Smalley, J. Phys. Chem. 1990,94, 8634; 14%: H.
Aiji, M. M. Alvarez, S. J. Anz. R. D. Beck, F. Diederich, K. Fostiropoulos,
D. R. Huffman, W. Kratschmer, Y. Rubin, K. E. Shriver, D. Sensharma.
R. L. Whetten. ibid. 1990, 94, 8630; 25.35%: F. Diederich, R. Ettl, Y.
Rubin, R. L. Whetten, R. Beck, M. M. Alvarez, S. J. Anz, D. Sensharma.
F. Wudl, K. C. Khemani, A. Kuch, Science 1991, 252, 548.
VCH Verlag~grsellschuftmbH, W-6940 Weinheim, 1992
0570-083319211212-1641$3.50+ .25/0
[lo] K. Chatterjee, D. H. Parker, P. Wurz, K. R. Lykke, D. M. Gruen, L. M.
Stock, J. Org. Chrm. 1992, 57, 3253; K. C. Khemani, M. Prato. F. Wudl,
ibid. 1992, 57, 3254.
[ l l ] A. M. Vasallo, A. J. Palmisauo, L. S. K. Pang, M. A. Wilson, J. Chem. Soc.
Chem. Commun. 1992, 60
[12] M . S. Meier, J. P. Selegue, J. Org. Chem. 1992, 57, 1924.
[13] K. Jinno. K. Ydmamoto, T. Ueda, H. Nagashima. K. Itoh, J. C. Fetzer,
W. R. Biggs, J. Chromutogr. 1992, 594. 105.
1141 P.-M. Allemand, A. Koch, F. Wudl, Y. Rubin. F. Diederich, M. M. Alvarez. S. J. Anz, R. L. Whetten, J A m . Ci7em. Soc. 1991, 113, 1050.
[151 The chromatographic separation of 400 mg of extract on A1,0, is accomplished in 4-6 h; F. Diedericli (ETH Zurich). private communication
(Sept. 17, 1992).
1161 A. Giicel. M. Becker. D. Hammel. L. Mindach. J. Rider. T. Simon. M.
Wagner, K. Miillen, A n p w . Chrm. 1992. 104, 666; Angew. Chem. I n t . Ed.
Engl. 1992, 31. 644.
Arc meltmg furnace with generator LSG 400, E. Biihler, Tubingen, modified by exchanging the bottom plate with holders for the cathodes, improving the cooling system to include top cooling, and installing a modified
heat shield. Furnace diameter 250 mm, volume 18 L.
Wavelength of the laser for vaporization: 520 nm with 5 mJ pulse-' on an
area of 1 mm2. Wavelength of the laser for ionization: 193 nm with 5 mJ
pulse-' on an area of 1 mm'. Analyzer: Channel Plates, Hamamatsu,
R. E. Smalley, Acc. Chem. Res. 1992, 25,98; T. Wdkabayashi, Y Achiba,
Chem. P h y ~Leli. 1992, 190, 465; T. W. Ebbesen, J. Tabuchi. K . Tanigaki,
&id. 1992, 19t, 336; R. Kerner, K. A. Penson, K. H. Bennemann, EuropI7y.7. Leit. 1992. 19, 363.
G . Helmchen. B. Glatz, Ein uppurutrv rinfhchrs System und Saden hochster
Z-ennleishmng XI- prapuuatiwn Mitfeldruck-Fliirsigkeitschromuto~ruphie,
Universitit Stuttgart, 1978; E. Ade, G. Helmchen, G. Heiliyenmann, TeIruhedron Lett. 1980, 21, 1137.
Previously toliiene/acetonitrile was used in a ratio of 1 : 1 for HPLC separations: F. Diederich, R. L. Whetten. C. Thilgen. R. Ettl, I. Chao, M. M.
Alvarez, Science 1991. 254, 1768.
Spectra! graphite from the company Ringsdorffwerke GmbH, Bonn-Bad
Godesberg (FRG), 6.15 x 305 mm.
Glass columns as described in ref. (201. Single metering pump FCI with
pump-head KllO and 0.2 L pulse damper. LEWA, Leonberg (FRG).
50 mL sample injection tube and UV detector 87.00 (detection wavelength
300 nm), Knauer. Berlin.
Note added in proof (9.11.92): W. A. Serivens, P. V. Bedworth. J. M.
Tour. J. Am. Chen?. Sol. 1992,114. 7917, reported the separation ofgrdm
amounts of C,, by flash chromatography on activated charcoal (NoriteA)/silica gel mixtures with toluene.
The First Stibepine: Synthesis and Structure of
Sb-C hlorobenzo(d]stibepine* *
By Arthur .J Ashe Ill,* Lukas Goossen, Jeff W. Kampf,
and Hisatoshi Konishi
Dedicated to Professor Kenneth B. Wiberg
on the occasion of his 65th birthday
Fully unsaturated seven-membered ring heterocycles containing Group 15 and 16 elements are of substantial interest.
The well-studied azepines l a and oxepines 2a"' are relatively
stable compounds in contrast to their heavier homologues,
phosphepines lbf2] and thiepines 2b,[3J for which most
derivatives are thermally labile towards heteroatom extrusion. Derivatives of selenepine 2cr4]and tellurepine 2dc5'
have been reported recently, while the labile As-phenylbenzo[darsepine (3) has been detected at low temperature by
spectroscopy.r2a1We report here on the first synthesis of benzo[djstibepines and the structural characterization of Sbchlorobenzo[djstibepine (5).r61
Prof. Dr. A. J. Ashe 111, L. Goossen, Dr. J. W Kampf, Dr. H . Konishi
Department of Chemistry. The University of Michigan
Ann Arbor. MI 48109-1055 (USA)
This work was supported by the Research Corporation and the donors of
the Petroleum Research Fund, administered by the American Chemical
( i VCH Verlag.~~esells~haji
nzhH, W-6940 Weinheik, 1992
2 a . E'=O
C . E'= Se
d . E'= Te
3.R = C6H5
9. R = C1
The reaction of dibutylbenzo[dstannepine (4)['1 with one
equivalent of SbCl, in CHCI, at 0 "C affords 5 and dibutyltin
dichloride, which may be removed by extraction with pentane. Recrystallization from diethyl ether/CH,CI, affords 5
as well-formed yellow crystals. Compound 5 may be converted to the alkyl derivatives 6 and 7 by treatment with MeLi
and BuLi, respectively. A11 the above operations must be
performed at low temperature since benzo[djstibepines are
thermally labile, forming naphthalene 8 and unidentified antimony-containing products. The conversion of 6 and 7 to 8
in CDC1, at 25 "C was monitored by 'H NMR spectroscopy
and showed first-order kinetics with t , , 2 = 370 and 660 min,
For comparison we have also examined benzo[d)arsepines.
The reaction of 4 with AsCI, in CHCI, gave 9 and Bu,SnCl,.
It was not possible to separate these products, but the identity of 9 was established by the similarity of its NMR spectra
of those of 5. In CDCl, 9 decomposes to form 8 with
t1,2 = 50 min at 25 "C. Thus, surprisingly, the arsepine is
more labile than the stibepine.
Since prior structural data on the heavier heteroepines was
available only for derivatives of t h i e ~ i n e ,it~was
~ ] of interest
to determine the crystal structure of a benzostibepine. The
structure of 5[81illustrated in Figure 1 shows a boatlike
stibepine ring. This boat conformation has angles of 41.7
Fig. 1 . Solid-state structure of 5 (ORTEP). Important distances [A] and angles
["I: Sbl-CI1 2.403(1); Sbl-C1 2.116(4); Sbl-C102.116(4);Cl-C2 1.325(5),
C2-C3 1.476(5); C8-C9 1.470(5), C9-ClO 1.320(6); CI1-Sh-C1 92.6(1), CI1Sb-CIO 93.6(1), C1-Sbl-C10 S9.9(1).
0570-0833/9211212-16423 3 . 5 0 i ,254)
Angew. Chem. Int. Ed. Engl. 1992, 31, N o . 12
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production, separating, fullerenes, optimization
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