Comparison Between [FeIV (O) (TMC) (NCMe)]2+ and [FeIV (O) (TMCS)]+ Non-heme Complexes of Geometric, Electronic Structures, Bonding and Reactivities

Density functional theory(DFT) calculations were carried out to elucidate the electronic structures, Fe-O bondings and reactivities of six-coordinated [F-IV(O) (TMC) (NCMe)](2+) and [Fe-IV (O) (TMCS)](+) complexes. The geometric parameters calculated by a hybrid functional UB3LYP with LanL2DZ(Fe) and TZV (rest) basis set were in agreement with the experimental data. Analysis of the orbital coefficients and the bond orders showed that the TMC ligand does not have any equivalent orbitals that are affecting the Fe-O pi bond. Due to the strong mixing of the iron 3d orbitals with the sigma orbital of the thiolate ligand orbitals and a much less mixing with the acetonitrile as an axial ligand, the electronic properties of [Fe-IV (O) (TMC) (NCMe)](2+) and [Fe-IV (O) (TMCS)](+) are different and the Fe-O bond length of the [Fe-IV (O) (TMCS)](+) complex is longer than that of the [Fe-IV (O) (TMC) (NCMe)](2+) complex.