Electrophilic aryl C–H amination by dimetal nitrides: correlating electronic structure with reactivity

Abstract

Using density functional methods we have modelled the intramolecular electrophilic aryl C–H amination for 15 dimetal nitrides, both homo- and heteronuclear, along with 2 mononuclear nitrides, in the pursuit of understanding the reactivity of the dimetal nitrido Ru₂(DPhF)₄N (DPhF = N,N′-diphenyl formamidinate) molecule, for which this amination reaction was experimentally observed and characterized. It was found that the 3-center bonding manifold (MMN) that arises between the metal–metal bond and axial nitrido moiety has a dominant influence in the electronic structure and consequently the reactivity at each step in the reaction. It was found that transition state energetics correlate strongly with product stabilization and that these quantities depend on the number of electrons available to occupy the MMN manifold. As the reaction proceeds the number of orbitals in the manifold decreases by one and the point at which this happens determines which of two transition states is rate limiting. The dimetallic nitrides are shown to be inherently more reactive than the mononuclear complexes and so the MMN manifold that is only active in the dimetallic complexes comes through as an important factor in facilitating this amination reaction. Overall, a strong correlation between electronic structure and reactivity is established for C–H amination and new synthetic targets are proposed to develop new facets of this reactivity.