Joint Molecular Mechanics and Atom−Atom Pair Potential Computations on the Solid State Dynamics of [Fe₃(CO)₁₂]¹

The solid state dynamics of Fe3(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° in-plane jumps of the Fe3 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” 13C NMR chemical shifts at that temperature.