SIMULATION OF THE MOLECULAR AND ELECTRONIC-STRUCTURE OF HETEROFULLERENES C55Y5 (Y = SI, GE, SN, B, AL, N, P, SIH, GEH, SNH) AND THEIR ETA(5)-PI-COMPLEXES WITH LI BY THE MNDO METHOD

Qualitative estimates of the relative stability of hypothetical hetero fullerenes C55Y5 (Y = Si, Ge, Sn, B, Al, N, P, SiH, GeH, SnH) and some eta(5)-pi-complexes LiC55Y5 were carried out by the MNDO method. Atom s Y (or groups XH) are assumed to substitute those C atoms in fulleren e C-60 which are located at the alpha-positions of a separated pentago nal face (pent) of this polyhedral molecule. It is shown that the spi n densities in radicals C,,Y, (Y = SiH, GeH, SnH, B, Al, N, P) are loc alized on the separated pentagon atoms and the Li-pentagonal face (Li- pent) bonds in eta(5)-pi-complexes of these radicals with the Li atom are considerably stronger than the Li-pent bonds in complexes [ pi-L iC60](+) and [eta(5)-pi-LiC60] of unsubstituted C-60. In addition, it is established that the Li-pent bond energies in eta(5)-pi-complexes LiC55B5 and Li55Al5 exceed the energy of the Li-pent bond in the eta( 5)-pi-complex LiC60H5 studied earlier. In contrast, the energies of si milar bonds for Y = N, P are close to the energy of the Li-pent bond in the eta(5)-pi-complex LiC60H5. (C) 1998 Elsevier Science S.A. All r ights reserved.