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

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.