Joint molecular mechanics and atom-atom pair potential computations on the solid state dynamics of [Fe-3(CO)(12)]

The solid state dynamics of Fe-3(CO)(12) has been interpreted on the basis of molecular mechanics computations within the crystal lattice. The dynamic process, frozen out at 180 K and responsible for the NMR coalescence at 220 K, consists of 60 degrees inplane jumps of the Fe-3 triangle within the ligand envelope. At variance, large libration about the three bisectors of the triangle are not frozen out at 180 K and are responsible for the ''anomalous'' C-13 NMR chemical shifts at that temperature.