Transition-metal C-60 bonding by guided ion beam scattering

Ion beam scattering techniques are used to examine interactions of transiti on-metal ions with C-60 over the collision energy range from 1-100 eV. The metals studied are iron, manganese, chromium, molybdenum, and tungsten. For each metal ion, in addition to charge transfer and dissociative charge tra nsfer, two distinct types of MC60+ complexes are observed. One forms with n o activation barrier at low collision energies, is weakly bound (1-3 eV), a nd always decomposes by loss of metal. We attribute this to an exohedral co ordination complex, as has been proposed by others who have seen this type of complex. A second type of MC60+ complex is observed at collision energie s above similar to 10 eV. This high energy complex has a substantial activa tion barrier to formation, is chemically bound, and decomposes by loss of m etal dicarbide (MC2) or metal. We propose that this complex is a network bo und structure, with the metal atom probably sitting above the fullerene sur face, chemically bound to two or more carbon atoms. (Int J Mass Spectrom 18 5/186/187 (1999) 603-615) (C) 1999 Elsevier Science B.V.