Two-fold proton coupled electron transfer of a Ta(V) aniline complex mediated by a redox active NNN pincer ligand

The proton coupled electron transfer reactivity of an octahedral Ta(V) aniline complex ligated by an acridane-derived redox active NNN pincer ligand is reported. Reversible association of aniline to a Ta(V) dichloride leads to significant coordination induced bond weakening of aniline’s N–H bonds allowing for two-fold hydrogen atom abstraction yielding a terminal imido complex accompanied by two-electron oxidation of the NNN pincer ligand under retention of the metal oxidation state. The bond dissociation free energies of the amine and a transient radical amido complex are estimated via stoichiometric reactions with hydrogen atom abstractor and donor reagents complemented by DFT calculations.