Where to draw the line in defining a molecular structure

It is the purpose of this paper to demonstrate how the theory of atoms in molecules (AIM) can be used to complement molecular orbital models to obtain an increased understanding of molecular structure and reactivity. The oxidative addition reaction of a hydrosilane with a Mn cyclopentadienyl dicarbonyl fragment, a common constituent of a large class of organometallic complexes, provides an ideal vehicle for demonstrating the ability of AIM to not only define structure but to predict its possible instabilities, as well as recovering the rationalizations of frontier orbital theory regarding the susceptibility and mode of attack encountered in the addition reaction.