Isolation of a Square Pyramidal Bis(amidophenolate)‐Supported As(III)‐Cation: Coordination‐Induced Electromerism at As

Abstract The synthesis and structural characterization of a slightly distorted square pyramidal arsenium cation is reported. Spectroscopic, crystallographic, and computational evidence indicate that coordination of typical Lewis bases to the As(III)‐center induces its oxidation to As(V) with concomitant reduction of the supporting, redox‐active bis(amidophenolate) ligand. That reaction is reversible and represents a well‐defined example of base‐induced electromerism in an As‐complex. Single electron reduction of the same As(III) species initially generates a ligand‐centered radical, which is persistent enough to be observed by EPR but slowly decays to a heterodimer. Preliminary experiments demonstrate the utility of the As(III)‐cation as initiator for transfer hydrogenation reactions.