Sequential one-electron redox processes in a homoleptic rhodium complex supported by a bis(sulfidophosphoranyl)triazine pincer framework

The stabilization of open-shell configurations in rhodium chemistry remains challenging because rhodium typically favors two-electron reactivity between the +I and +III oxidation states. Herein, we report a homoleptic Rh(III) complex supported by two bis(sulfidophosphoranyl)triazine pincer ligands that enables access to multiple sequential one-electron reduction events. Spectroelectrochemistry and EPR demonstrate that the first reduction generates an S = 1/2 species featuring substantial metal–ligand spin delocalization, consistent with a non-innocent ligand framework. Subsequent reductions are accompanied by coordination reorganization and ligand dissociation, underscoring the dynamic redox behavior of the system and emphasizing the blurred boundary between metal- and ligand-centered redox processes. Overall, these results illustrate how a bis(sulfidophosphoranyl)triazine platform can promote multi-step one-electron redox chemistry in a mononuclear rhodium complex while revealing how redox-active ligands affect conventional oxidation-state descriptions.