Adsorption of ${\mathrm{C}}_{60}$ on nickel clusters at high temperature

The adsorption of ${\mathrm{C}}_{60}$ on nickel clusters has been studied in a flow-tube reactor at temperatures between 823 and 1073 K. Saturation coverages of ${\mathrm{C}}_{60}$ have been determined for ${\mathrm{Ni}}_2{–\mathrm{Ni}}_{72}$ and show a size dependence consistent with ${\mathrm{C}}_{60}$ adsorption on essentially spherical ${\mathrm{Ni}}_n$ clusters. There is no evidence for ${\mathrm{C}}_{60}$ decomposition. The configuration of the adsorbed ${\mathrm{C}}_{60}$ molecules appears to change from $\mathrm{tetrahed}$$\mathrm{ra}\overrightarrow{l}\mathrm{octahedra}\overrightarrow{l}\mathrm{cubi}\overrightarrow{c}\mathrm{less}$ symmetrical arrangements as metal cluster size increases. An RRK modeling of the first ${\mathrm{C}}_{60}$ that binds to the nickel clusters yields a binding energy in excess of 2.06 eV. The binding energy appears to decrease with decreasing metal nuclearity of the binding site, with binding to atop sites on the ${\mathrm{Ni}}_n$ clusters being relatively weak. It is argued that electron transfer to the ${\mathrm{C}}_{60}$ ligands is limited by charging of the central ${\mathrm{Ni}}_n$ core and that this may provide a way of controlling the extent of electron transfer to the adsorbed molecules.