Proton-Coupled Electron Transfer at the Pu Couple.

The synthesis and solution and solid-state characterization of [Pu(NPC)], , (NPC = [NPBu(pyrr)]; Bu = C(CH); pyrr = pyrrolidinyl) and [Pu(NPC)][K(2.2.2.-cryptand)], , is described. Cyclic voltammetry studies of reveal a quasi-reversible Pu couple, an irreversible Pu couple, and a third couple evincing a rapid proton-coupled electron transfer (PCET) reaction occurring after the electrochemical formation of Pu. The chemical identity of the product of the PCET reaction was confirmed by independent chemical synthesis to be [Pu(NPC)(HNPC)][B(ArF)], , (B(ArF) = tetrakis(2,3,4,5,6-pentafluourophenyl)borate) via two mechanistically distinct transformations of : protonation and oxidation. The kinetics and thermodynamics of this PCET reaction are determined via electrochemical analysis, simulation, and density functional theory. The computational studies demonstrate a direct correlation between the changing nature of 5 and 6 orbital participation in metal-ligand bonding and the electron density on the N atom with the thermodynamics of the PCET reaction from Np to Pu, and an indirect correlation with the roughly 5-orders of magnitude faster Pu PCET compared to Np for the An species.