Theoretical estimates of the η 6 bonding capability of buckminsterfullerene in transition metal complexes

Abstract

In order to provide a quantitative description of the relative ability of C 60 to bond as an η 6 ligand, arene exchange energies for tricarbonyl(arene)chromium systems were calculated using the method of partial retention of diatomic differential overlap (PRDDO). This represents the first theoretical estimate of the relative affinity of C 60 as an η 6 ligand, and results indicate that C 60 is an inferior ligand compared to benzene. The arenes considered included benzene, chlorobenzene, p-difluorobenzene, and buckminsterfullerene. The exchange of benzene for C 60 as an arene ligand is calculated to require 19 kcal/mol, but this can be reduced by modifying the exchanging ligand. Reduced overlap from C 60 hybrid orbitals is found to be partly responsible for less favorable η 6 bonding, which suggests that larger metals such as tungsten may be better able to bond in an η 6 fashion to C 60.