Coordination Chemistry of a Strongly-Donating Hydroxylamine with Early Actinides: An Investigation of Redox Properties and Electronic Structure

Separations of f-block elements are a critical aspect of nuclear waste processing. Redox-based separations offer promise, but challenges remain in stabilizing and differentiating actinides in high oxidation states. The investigation of new ligand types that provide thermodynamic stabilization to high-valent actinides is essential for expanding their fundamental chemistry and to elaborate new separation techniques and storage methods. We report herein the preparation and characterization of Th and U complexes of the pyridyl-hydroxylamine ligand, N-tert-butyl-N-(pyridin-2-yl)­hydroxylamine (pyNO^–). Electrochemical studies performed on the homoleptic complexes [M­(pyNO)₄] (M = Th, U) revealed significant stabilization of the U complex upon one-electron oxidation. The salt [U­(pyNO)₄]⁺ was isolated by chemical oxidation of [U­(pyNO)₄]; spectroscopic and computational data support assignment as a U^V cation.