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Nitrene transfer reactions are increasingly used to access various kinds of amine derivatives but the underlying mechanisms have not been unraveled in most cases. Fe-catalyzed aziridination of alkenes has appeared as a promising route to aziridines which are important derivatives both per seand as intermediates in many synthetic procedures. We report the strong activity and the mechanism of di-iron catalysts for aziridination of styrenes using phenyltosyliodinane (PhINTs). In addition, we have developed a similar mono-iron catalyst which operates under the same mechanism albeit with a reduced activity. DFT calculations were performed to investigate the structure and electronic structure of the FeIVNTs species of the latter catalyst. They suggest that the reaction pathway leading to the nitrene transfer to the olefin involves a transient charge transfer on the way to a radical intermediate, which is totally consistent with the experimental results. Moreover, these calculations identify the electron affinity (EA) of the active species as one key parameter allowing rationalization of the observations, which opens the way to improving the catalyst efficiency on a rational basis.

Density functional theory calculations have been performed to calculate the one-electron redox potential for a series of oxoiron(IV) porphyrin complexes of the form [(TMP)FeIV(O)(L)] (TMP = 5,10,15,20-tetramesitylporphyrinate). Different axial ligands were chosen (L = none, Im, ClO4–, CH3CO2–, Cl–, F–, SCH3–) in order to compare the results with recent electrochemical experiments. The redox potentials were calculated with a Born–Haber cycle and the use of an internal reference, i.e. the absolute redox potential of ferrocene. Diverse methodologies were tested and show that the computed redox potentials depend strongly on the functional, the basis set, and the continuum models used to compute the solvation energies. Globally, BP86 gives better results for the geometries of the complexes than B3LYP and M06-L as well as more consistent values for the redox potentials. Although the results fit the experimental data for L = Im and L = ClO4–, the addition of the other anionic axial ligands to the oxoiron(IV) porphyrin complex strongly lowers the redox potential, which is in disagreement with experimental observations. This important discrepancy is discussed.

The mechanisms of the reduction of four isoelectronic heteroallenes (CS2, COS, PhN3, and PhNCO) by trivalent uranium complex (MeC5H4)3U were determined by using DFT methods. The experimental formation of either the bimetallic CS2and the PhNCO uranium(IV) adducts or the bimetallic sulfide complex (COS) and the monometallic uranium(V) phenylimide complex (PhN3) were rationalized. The formation of the products was explained by a unique reaction mechanism with a uranium(IV)‐bridged heteroallene intermediate.

The ligand is the key: A DFT study of the formation of uranium(IV) formaldehyde through a transient uranium(IV) Schrock‐type carbene intermediate shows the importance of the ligand in stabilizing the transition state of the carbeneoxygen coupling (see scheme).