Depicting electronic distributions from accurate computational first principles: On the relationship between the complex patterns of bonding interaction and the back-donation phenomenon

Abstract

A detailed theoretical description of metal?ligand interactions in the case of the simple isoelectronic transition metal series Ni, Cu+, Zn2 and one C2H4 ligand is presented. This task is performed in terms of the local and nonlocal topology-based formalisms of the electronic density and its decomposition into paired and unpaired contributions. The analysis is mainly focused on the nature of the carbon?metal interactions under the traditional chemical back-donation phenomena and the relationship with the existence of two-electron three-center (2e-3c) complex patterns of bonding, that is, 2e-3c atomic interactions. For these simple prototypical systems, which seem to be adequate examples to describe the topologic features of such electron distribution in terms of the density point of view, both phenomena, that is, the back-donation and the 2e-3c interactions, are mutually exclusive.