Fate of Oxidation States at Actinide Centers in Redox‐Active Ligand Systems Governed by Energy Levels of 5 f Orbitals.

We report the formation of a NpIV complex from the complexation of NpVIO22+ with the redox‐active ligand tBu‐pdiop2−=2,6‐bis[N‐(3,5‐di‐tert‐butyl‐2‐hydroxyphenyl)iminomethyl]pyridine. To the best of our knowledge, this is the first example of the direct complexation‐induced chemical reduction of NpVIO22+ to NpIV. In contrast, the complexation of UVIO22+ with tBu‐pdiop2− did not induce the reduction of UVIO22+, not even after the two‐electron electrochemical reduction of [UVIO2(tBu‐pdiop)]. This contrast between the Np and U systems may be ascribed to the decrease of the energy of the 5 f orbitals in Np compared to those in U. The present findings indicate that the redox chemistry between UVIO22+ and NpVIO22+ should be clearly differentiated in redox‐active ligand systems. [ABSTRACT FROM AUTHOR]