Fullerenes endohedral fullerene complexes

Since the discovery by Kratschmer and Huffman last year of a simple method for producing macroscopic quantities of Cjo, C70, and some of the higher empty fullerenes, we have searched for a means of extending this technique to fill the void and make macroscopic quantities of internally substituted fullerenes— endohedral fullerene complexes. We report below our first success in this search. It involves a simple revision to the laser-vaporization method originally used in 1985 just do it in an oven at 1200 C. 

One particularly striking aspect of endohedral fullerene complexes is the surprising ability of the carbon cage to contain highly reactive species such as atomic nitrogen.1801 N C6o (54) has been prepared... 

The production of endohedral fullerene complexes in visible amounts was first accomplished by a pulsed laser vaporization of a lanthanum oxide-graphite composite rod in a flow of argon gas at 1200 °C [66]. In this procedure, the newly formed endohedrals, together with empty fullerenes, sublime readily and are carried away in the flowing gas, depositing on the cool surfaces of the apparatus. This sublimate contains the complexes La CgQ, La C74 and La Cg2 (Figure 1.9). Among these, the endohedral molecule La Cg2 exhibits an extra stability. It can... 

Endohedral Fullerene Complexes, Nanotubes and Other Fullerene-based Supramolecular Systems... 

One of the most remarkable properties of fullerenes is their ability to encapsulate atoms, ions and small molecules, to form the so-called endohedral fullerene complexes, denoted... 

Figure 15.30 X-ray crystal structure of a derivative of the endohedral fullerene complex Sc3N C80 (Sc and N atoms shown as large spheres).51...

C. G. Joslin, C. G. Gray, and S. Goldman, Chem. Phys. Lett., 227, 405 (1994). Infrared Rotation and Vibration-Rotation Bands of Endohedral Fullerene Complexes. Helium in C60-Derived Nanotubes. 

Dodziuk, H., Nowinski, K.S. Topological isomerism should rotaxanes, endohedral fullerene complexes and in-out isomers of perhydrogenated fullerenes be considered as such Tetrahedron 54 (1998), 2917-2930. 

Endohedral metal fullerenes can be detected in relatively small amounts in the mass spectra in the laser vaporization cluster beams (vide supra). However, macroscopic quantities of these compounds may be produced rather readily either by vaporization in a laser furnace apparatus or by arc-burning of a composite rod of graphite and the corresponding metal oxide. In Fig. 4.50, a mass spectrum which illustrates the formation of a series of fullerene endohedral yttrium complexes obtained by laser vaporization of a composite graphite/ Y2O3 rod at 1200 ""C is reproduced. Among these species there is also one, Y2 Cs2, which corresponds to the inclusion of a metal cluster in the fullerene ball. 

This review covers all organometallic complexes of Sc, Y and the lanthanides reported in the year 2000 and their reactions. Endohedral fullerene complexes of the lanthanides have, as usual, been excluded. Highlights this year include striking reports of lanthanides in non-classical oxidation states (Sections 3.2 and 5), a remarkable reversible dinitrogen activation described in Section 3.9.2 and evidence for the existence of the divalent hydrides LnH2(THF)2 (Ln = Sm, Yb) (Section 3.10). In addition Evans has assessed the utility of electrospray mass spectrometry for the characterization of organolathanides. The results are promising and the spectra and dissociation patterns show sensitivity to the metal and its oxidation state. ... 

Y. Rubin, Ring Opening Reactions of Fullerenes Designed Approaches to Endohedral Metal Complexes , Top. Curr. Chem. 1999,199, 67-91. 

The Complexes Involving Induced Fit and Without It Endohedral Fullerene, Hemicarcerand and Soft Rebek s Tennis Ball-Like Hosts... 

Exohedral metal complexes [C6qM]+ are formed by the reaction of Ceo with naked M+ ions (M = Fe, Co, Ni, Cu, Rh, La). ForNi+ the bis-fullerene complex [(C6o)2Ni]+ was also observed. In contrast to the endohedral fullerenes, excitation of these complexes results in facile metal elimination with no associated cage fragmentation. 

The endohedral fullerenes U C28 and U C6o have been reported to be sufficiently stable to allow chemical isolation. Endohedral complexes of the smaller fullerenes (C2 , 2n < 60) are conunonly observed in molecular beam experiments (Section 4.1), but this stabilization of C28 by uranium atom encapsulation is remarkable. A theoretical study of [7i-C28]" and Td-C2iiU (25) indicate that they are stable molecules, and that the laboratory preparation of their derivatives may be viable. ... 

Structural Proposetls for Endohedral Metal-Fullerene Complexes, Chem. Phys. Lett. 187, 1-7 (1991). 

Gi92 E. G. Gillan et at., Endohedral Rare-Earth Fullerene Complexes, J. Phys. Chem. 96, 6869-6871 (1992). 

Rubin, Y. Parker, T.C. Kahn S.I. Holliman, C.L. McElvany S.W. Precursors to endohedral metal fullerene complexes synthesis and x-ray structure of a flexible macrocyclic acetylenic cyclophane CgiH h- J. Am. Chem. Soc. 1996, 35(22), 5308-5309. 

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