Electronic structure and coordination chemistry of phenanthridine ligand in first-row transition metal complexes: A DFT study

The geometric parameters, electronic structures, and haptotropic migration of a series of hypothetical compounds of general formula CpM(C13H9N) and (CO)3M(C13H9N) (M = fist row transition metal, Cp = C5H5, and C13H9N = phenanthridine ligand) are investigated by means of the density functional theory. The phenanthridine ligand can bind to the metal through η1 to η6 coordination mode, in agreement with the electron count and the nature of the metal, showing its capability to adapt itself to the electronic demand of the metal as well as to the polycyclic aromatic hydrocarbons. In the investigated species, the most favored closed‐shell count is 18‐electron except for the Ti and V models which are deficient open‐shell 16‐electron configuration. This study has shown the difference in coordination ability of this heteropolycyclic ligand: the coordination of the central C5N ring is less favored than the terminal C6 rings, in agreement with the π‐electron density localization. Most of the investigated complexes are expected to exhibit a rich fluxional behavior. This flexibility favors the possibility for the existence of several isomers as well as their interconversion through haptotropic shifts. © 2012 Wiley Periodicals, Inc. The origin of the very rich coordination chemistry of phenanthridine can be explained in large part due to the very large electronic and structural flexibility of this molecule, which is able to adapt to the electronic demand of the metal. The C6 and C5N rings of phenanthridine can be coordinated in various hapticities, depending on the nature of the ML n moiety. This flexibility favors the possibility of existence of several isomers of comparable energy.