10430
J. Am. Chem. Soc. 1999, 121, 10430-10431
The impetus for this work derived from the observation that
hydrocarbon 1 underwent explosive decomposition at 245 °C to
generate CH4, H2, and graphitized carbon particles.8 While the
latter were formed in low yield (1-2% by TEM), in poor quality,
and in the presence of mainly graphite and amorphous carbon, it
suggested the possibility of a general approach to such carbon
allotropes. Initial investigations in this vein were, however,
disappointing inasmuch as the less complex analogues of 1,
namely 2,8 3,9 4,10 (phenylethynyl)-, and ethynylbenzene, while
also decomposing explosively on heating with emission of light
and gases, did not furnish nanotubes or onions, but only some
graphite and mainly amorphous carbon. Annealing the samples
in an oven at 800 °C for 6 h increased the graphitized areas, but
only marginally. A more detailed investigation of 2, the “mono-
meric” precursor to 1, revealed its explosion point at 141 °C,
with a sharp irreversible DSC exotherm (∆Hrxn ) -53 kcal
Metal Encapsulating Carbon Nanostructures from
Oligoalkyne Metal Complexes
Peter I. Dosa, Christoph Erben, Vivekanantan S. Iyer,
K. Peter C. Vollhardt,* and Ian M. Wasser
Department of Chemistry, UniVersity of California at Berkeley
and the Chemical Sciences DiVision
Lawrence Berkeley National Laboratory
Berkeley, California 94720-1460
ReceiVed July 13, 1999
Carbon nanotubes, onions, and related closed-shell carbon
particles have commanded extensive recent attention because of
their potential applications as unique electronic, magnetic, and
mechanically robust materials.1 When filled with metals,2 such
nanocapsules have additional promise as magnetic particles,
contrasting agents, protecting cloaks, and catalysts and in other
applications.1,2 Among the various methods for their preparation,1
the transition metal (especially Fe, Co, and Ni) catalyzed pyrolysis
of small organic molecules has shown promise for larger scale
production and in structural control.3 While the use of organo-
metallic complexes as solid catalyst precursors4 or copyrolytic
gaseous ingredients1g,5 has been reported, all of these studies have
been limited to gas-phase experiments at relatively high temper-
atures. There is very little literature that deals with the organic
solid-state generation of carbon nanotubes.1a,e,g,6 The latter suffers
from extreme conditions, poor yields, or not readily modifiable
starting materials. Development of synthetic organic approaches
to closed shell large carbon structures is desirable but in its
infancy.7 Here we present a significant step in its progress.
(1) For very recent reviews, see: (a) Terrones, M.; Hsu, W. K.; Kroto, H.
W.; Walton, D. R. M. Top. Curr. Chem. 1999, 199, 189-234. (b) Ajayan, P.
M. Chem. ReV. 1999, 99, in press. (c) Smalley, R. E.; Yakobson, B. I. Solid
State Commun. 1998, 107, 597-606. (d) Ebbesen, T. W. Acc. Chem. Res.
1998, 31, 558-566. (e) Subramoney, S. AdV. Mater. 1998, 10, 1157-1171.
(f) Laurent, C.; Flahaut, E.; Reigney, A.; Rousset, A. New J. Chem. 1998, 22,
1229. (g) Journet, C.; Bernier, P. Appl. Phys. A 1998, 67, 1-9. (h) Rao, C.
N. R.; Govindaraj, A.; Sen, R.; Satishkumar, B. C. Mater. Res. InnoV. 1998,
2, 128-141. (i) Ebbesen, T. W. Carbon Nanotubes; CRC Press: Boca Raton,
FL, 1997.
(2) For reviews, see: (a) Ugarte, D.; Sto¨ckli, T.; Bonard, J. M.; Chaˆtelain,
A.; de Heer, W. A. Appl. Phys. A 1998, 67, 101-105. (b) Sloan, J.; Cook, J.;
Green, M. L. H.; Hutchison, J. L.; Tenne, R. J. Mater. Chem. 1997, 7, 1089-
1095.
(3) For very recent work, see, inter alia: (a) Sun, L. F.; Mao, J. M.; Pan,
Z. W.; Chang, B. H.; Zhou, W. Y.; Wang, G.; Qian, L. X.; Xie, S. S. Appl.
Phys. Lett. 1999, 74, 644-646. (b) Flahaut, E.; Govindaraj, A.; Peigney, A.;
Laurent, C.; Rousset, A.; Rao, C. N. R. Chem. Phys. Lett. 1999, 300, 236-
242. (c) Pan, Z. W.; Xie, S. S.; Chang, B. H.; Sun, L. F.; Zhou, W. Y.; Wang,
G. Chem. Phys. Lett. 1999, 299, 97-102. (d) Huang, Z. P.; Xu, J. W.; Ren,
Z. F.; Wang, J. H.; Siegal, M. P.; Provencio, P. N. Appl. Phys. Lett. 1998, 73,
3845-3847. (e) Cheng, H. M.; Li, F.; Su, G.; Pan, H. Y.; He, L. L.; Sun, X.;
Dresselhaus, M. S. Appl. Phys. Lett. 1998, 72, 3282-3284. (f) Hafner, J. H.;
Bronikowski, M. J.; Azamian, B. R.; Nikolaev, P.; Rinzler, A. G.; Colbert,
D. T.; Smith, K. A.; Smalley, R. E. Chem. Phys. Lett. 1998, 296, 195-202
and references therein.
(4) For a seminal paper, see: Mu¨ller, T. E.; Reid, D. G.; Hsu, W. K.; Hare,
J. P.; Kroto, H. W.; Walton, D. R. M. Carbon 1997, 35, 951-966.
(5) Limited to metallocenes and Fe(CO)5, see: (a) Satishkumar, B. C.;
Govindaraj, A.; Sen, R.; Rao, C. N. R. Chem. Phys. Lett. 1998, 293, 47-52.
(b) Cheng, H. M.; Li, F.; Brown, S. D. M.; Pimenta, M. A.; Marucci, A.;
Dresselhaus, G.; Dresselhaus, M. S. Chem. Phys. Lett. 1998, 289, 602-610
and references therein.
(6) See, inter alia: (a) Kroke, E.; Schwarz, M.; Buschmann, V.; Miehe G.;
Fuess, H.; Riedel, R. AdV. Mater. 1999, 11, 158-161. (b) Czerwosz, E.;
Dluzewski, P.; Dmowska, G.; Nowakowski, R.; Starnawska, E.; Wronka, H.
Appl. Surf. Sci. 1999, 141, 350-356. (c) Hsu, W. K.; Zhu, Y. Q.; Trasobares,
S.; Terrones, H.; Terrones, M.; Grobert, N.; Takikawa, H.; Hare, J. P.; Kroto,
H. W.; Walton, D. R. M. Appl. Phys. A 1999, 68, 493-495. (d) Grobert, N.;
Terrones, M.; Osborne, A. J.; Terrones, H.; Hsu, W. K.; Trasobares, S.; Zhu,
Y. Q.; Hare, J. P.; Kroto, H. W.; Walton, D. R. M. Appl. Phys. A 1998, 67,
595-598. (e) Harris, P. J. F.; Tsang, S. C. Chem. Phys. Lett. 1998, 293, 53-
58. (f) Stevens, M. G.; Subramoney, S.; Foley, H. C. Chem. Phys. Lett. 1998,
292, 352-356. (g) Kukovitskii, E. F.; Chemozatonskii, L. A.; L’vov S. G.;
Mel’nik, N. N. Chem. Phys. Lett. 1997, 266, 323-328. (h) Li, Y. L.; Yu, Y.
D.; Liang, Y. J. Mater Res. 1997, 12, 1678-1680. (i) Cho, W.-S.; Hamada,
E.; Kondo, Y.; Takayanagi, K. Appl. Phys. Lett. 1996, 69, 278-279.
mol-1),11 and, after heat treatment of the resulting black residue,
amorphous, carbon black like structures (TEM).1h Unlike 1, LDI-
TOF MS on thin films of 2 did not provide indications of a
measurable oligomerization process.
In contrast, thermolysis of the complexes 5-8 (for synthetic
and X-ray structural details, see Supporting Information) had a
dramatically different outcome, most strikingly for the cobalt
complexes 7 and 8. In all cases, a relatively smooth reaction
commenced below 200 °C, for the carbonyl compounds occurring
concomitant with the release of CO gas. For 8, DSC reveals again
a sharp exotherm (∆Hrxn ) -47 kcal mol-1) at 153 °C, followed
by a similar endotherm (+71 kcal mol-1) at 188 °C, both
irreversible. We believe the former to signal a rapid polymeri-
zation process (possibly induced by initial weak12 Co-Co bond
breaking), the latter to reflect the extrusion of (mainly) the CO
(7) See, inter alia: (a) Bunz, U. H. F.; Rubin, Y.; Tobe, Y. Chem. Soc.
ReV. 1999, 28, 107-119. (b) Berresheim, A. J.; Mu¨ller, M.; Mu¨llen, K. Chem.
ReV. 1999, 99, 1747-1785. (c) Faust, R. Angew. Chem., Int. Ed. Engl. 1998,
37, 2825-2828.
(8) Boese, R.; Matzger, A. J.; Vollhardt, K. P. C. J. Am. Chem. Soc. 1997,
119, 2052-2053.
(9) Haley, M. M.; Bell, M. L.; English, J. J.; Johnson, C. A.; Weakley, T.
J. R. J. Am. Chem. Soc. 1997, 119, 2956-2957.
(10) Behr, O. M.; Eglinton, G.; Galbraith, A. R.; Raphael, R. A. J. Chem.
Soc. 1960, 3614-3625. See also: Adams, R. D.; Bunz, U. H. F.; Fu, Wii;
Nguyen, L. J. Organomet. Chem. 1999, 578, 91-94.
(11) For DSC data of related alkynes, see refs 8 and 9 and the following:
Grubbs, R. H.; Kratz, D. Chem. Ber. 1993, 126, 149-157 and references
therein.
(12) Klingler, R. J.; Rathke, J. W. J. Am. Chem. Soc. 1994, 116, 4772-
4785.
10.1021/ja9924602 CCC: $18.00 © 1999 American Chemical Society
Published on Web 10/22/1999