Exohedral complexes

The corresponding calculations on the endohedral and exohedral complexes of CgQ with H, F or the methyl radical as guest predict the same behavior [98]. In all cases the formation of endohedral covalent bonds is energetically unfavorable due to the analogous strain arguments, even if such reactive species as F atoms are exposed to the inner surface of Cjq. 

Dendzik, Z., Kosmider, M., Dawid, A., et al. (2005). Interaction-induced depolarized light scattering spectra of exohedral complexes of Ne and Ar with fullerenes and nanotubes. Mater. Sci.-Poland, 23, 457—66. 

Fullerene-Organometallics. Also recently investigated are the organo-metallic exohedral complexes of osmium, ruthenium, and platinum which are readily attached to the external framework of the C o molecule by solution chemistry.I X I An osmylated-Ceo compound is shown in Fig. 15.8.P1]... 

The conclusions of the original experiment in which the Ceo La species were first observed [2] have proven less definitive than was hoped. The line of reasoning that led to the belief that the observed molecules were endohedral complexes was questioned by Cox and coworkers [13], who in a subsequent paper [14] concluded that the available experimental evidence did not prove conclusively that the lanthanum atom was indeed trapped inside the Ceo cage. This ambiguity has now been resolved thanks to a whole spectrum of experiments that provided further circumstantial evidence for the endohedral complexes [15], generated externally bound (exohedral) complexes and contrasted their properties with those of endohedral complexes [16], and generated and characterized endohedral complexes [17-21]. 

ENDOHEDRAL AND EXOHEDRAL COMPLEXES VITH THE LITHIUM AND SODIUM MONOCATIONS... 

The HF/DZP calculations presented in Table 9 also reveal that the exohedral complexes, i.e. the species with the lithium and sodium monocations located outside the Ceo cage, have energies significantly lower than their endohedral counterparts. The enhanced stability of the exohedral complexes is easily accounted for by noting that the endohedral potential is larger than the electrostatic potential at a comparable distance outside the host cage. However, these energy differences do not... 

The wavefunction of the enclosed N atom is influenced by subsequent exohedral adduct formation with one or more addends [134]. This is caused by the altered cage structure of the adducts. The analogous complexes N C7o and P Cgo are made similarly to NcaCgQ, by bombarding a thin layer of fullerene on a cathode with energy-rich N- or P-ions, respectively [135,136]. 

Bis-Bidentate Chelators Tetranuclear Chelate Complexes of Metal(II) Ions [(R2NH3)4n M4II(L1011)6 ] with Exohedral Guests... 

FIGURE 29 Drift-time distribution recorded for LaQo with injection energy of 400 eV. The curve shows the drift-time distribution calculated from the transport equation for ions in the drift tube. The arrows show the expected drift times for endohedral La( Qo and exohedral La(Qo) complexes. The mobility was calculated using a simple hard-sphere collision model. 

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. 

With the discovery of Ceo and other fullerenes see Carbon Fullerenes), it was not long before investigations into the possible reactions of fullerenes and iridium complexes were undertaken. Quite a variety of exohedral iridium fullerene compounds have been characterized including complexes of... 

Table 7. PM3 dipole moments, heats of formation and bond energies of exohedral and endohedral complexes of Cgo with H, F and the methyl radical (Me)...

The significant cavity size present in Cgg ( 3.5 A diameter) and other fuiierenes allows practically any element of the periodic table to be incorporated inside them (Fig. 1). Endohedral complexes of fuiierenes are represented as Mj C2n, where the symbol denotes that the metal M is encapsulated within the carbon cage, in contrast to being attached outside (exohedral) or incorporated within the shell (heterohedral, see pp. 93 this volume. 

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