Product Variation in Reactions of MI₃(thf)₄ with Bis(Mesitoyl)Phosphide Across the M = U, Np, Pu Series

A series of reactions using sodium bis(mesitoyl)phosphide (^<b>Mes</b><b>BAP</b>^<b>-</b>) with the actinide starting material AnI₃(thf)₄ (An = U, Np, Pu) as well as the analogous reaction with CeI₃(thf)₄ was performed. Similar U and Np <b>An(</b>^<b>Mes</b><b>BAP)</b>_<b>4</b> (An = U, Np) products were obtained in the +4-oxidation state. The thorium homologue was synthesized using ThI₄(dme)₂ to generate <b>Th(</b>^<b>Mes</b><b>BAP)</b>_<b>4</b>, which was employed as a diamagnetic and predominantly redox inert metal center for comparison. The resulting product isolated from the analogous reaction with PuI₃(thf)₄ was <b>[Na(thf)][Pu(</b>^<b>Mes</b><b>BAP)</b>_<b>4</b><b>]</b>, where the metal coordinated four ligands and retained the +3-oxidation state. This result is distinct from that obtained from the reaction with CeI₃(thf)₄, where the Ce³⁺ product was <b>Ce(</b>^<b>Mes</b><b>BAP)</b>_<b>3</b><b>(thf)</b>_<b>2</b>. The compounds were isolated and characterized by X-ray diffraction, ultraviolet-visible (UV-vis)-nIR and NMR spectroscopies, and cyclic voltammetry. The synthetic results reveal how different redox stabilities across the 5f series can result in divergent reactivity of Pu. Electrochemical experiments produced redox features that suggest the potential to form reduced complexes supported by the ^<b>Mes</b>BAP ligand framework.