A pyracylene model for the interaction of transition metals with fullerenes: a density functional study

Abstract

Pyracylene, a polynuclear aromatic hydrocarbon which is made up of two benzene and two cyclopentadienyl rings, has been employed as a model to study the interaction of transition metal complexes with fullerenes. To reproduce adequately the geometric and electronic structure of fullerene with a pyracylene model, we had to impose suitable geometric constraints forcing the pyramidalisation angle on the two central carbon atoms to assume a value similar to that observed in C₆₀. Density functional calculations were then performed on (PH₃)₂M(C₁₄H₈) (M = Ni, Pd, Pt) molecules. The results have been analysed in terms of the Chatt–Dewar–Duncanson model and show that the constrained pyracylene is a fairly good model to study the interaction of transition metals with fullerene: geometries are reproduced within 0.02 Å and the bond dissociation energies are slightly underestimated by only 10–40 kJ mol⁻¹.