Metal-ring interactions in actinide sandwich compounds: A combined normalized elimination of the small component and local vibrational mode study

The relativistic Hamiltonian Normalised Elimination of the Small Component with atomic unitary transformation (NESCau) was used for the first time to calculate geometries and harmonic vibrational frequencies of actinide sandwich compounds (An: Th, Pa, U, Np, Pu; ). In addition, the Local Vibrational Mode analysis, the Natural Bond Orbital analysis, and the Atoms in Molecules analysis were applied to quantitatively assess the intrinsic strength and the nature of the An-ring interactions. Our results show that actinide sandwich compounds prefer strong covalent interactions between actinide and carbon atoms, similar to those found for homologous ferrocene-type complexes . The metal centre rather than the ring size plays a key role in the strength of those interactions.