What is the nature of bonding in [Fe(CO)3(NO)]− and [Fe(CO)4]2−?

Abstract

To shed new light on the electronic structure of [Fe(CO)3(NO)]¯ complex ion, DFT-based analysis of the nature of chemical bonding has been performed. For this purpose, the extended transition state energy decomposition analysis alongside the natural orbitals for chemical valence has been used and results are compared to the nature and the strength of the interactions in isoelectronic [Fe(CO)4]2− complex ion. Based on orbital contribution to the interaction energy and charge flow between the fragments, the ground state can be best described as an open-shell singlet with zero formal oxidation state on iron and negative charge on the nitrosyl ligand. It is in agreement with the different nature of interactions when NO+ and CO ligands are bonded to Fe(−II).