–Coordinations Revisited: An ELF Study of Ferrocene and Dibenzenechromium

Motivation. The chemistry of five–membered and six–membered conjugated cyclic ligands complexes belongs to the most important classes of organometallic compounds. The determination of the precise nature of the metal–ligand bond is of great importance for the synthesis of new compounds and understanding of their reactivity. We propose here a topological ELF analysis of the metal–ligand interaction with a comparative model study of K 5 – and K 6 –coordination respectively in ferrocene and dibenzenechromium. Method. Electron Localization Function (ELF) offers a reliable measure of electron pairing and localization. An ELF calculation partitions molecular space in terms of attractors and basins. Each basin, located around an attractor, could be clearly identify into series, each of then having a precise significance (core, lone pair, two– center bond, three–center bond, …). Results. This work shows that both K 5 – and K 6 –coordinations could be decomposed in a sum of K 1 – and K 2 – interactions, the latter being predominant. The bonding description is in agreement with the classical resonance scheme. Conclusions. The topological analysis of the ELF function provides a basis for interpreting and visualization of the bonding scheme in model sandwich molecules.