Unusual Actinyl Complexes with a Redox-Active N,S-Donor Ligand.

Understanding the fundamental chemistry of soft N,S-donor ligands with actinides across the series is critical for separation science toward sustainable nuclear energy. This task is particularly challenging when the ligands are redox active. We herein report a series of actinyl complexes with a N,S-donor redox-active ligand that stabilizes different oxidation states across the actinide series. These complexes are isolated and characterized in the gas phase, along with high-level electronic structure studies. The redox-active N,S-donor ligand in the products, C 5 H 4 NS, acts as a monoanion in [U VI O 2 (C 5 H 4 NS - )] + but as a neutral radical with unpaired electrons localized on the sulfur atom in [Np V O 2 (C 5 H 4 NS • )] + and [Pu V O 2 (C 5 H 4 NS • )] + , resulting in different oxidation states for uranium and transuranic elements. This is rationalized by considering the relative energy levels of actinyl(VI) 5f orbitals and S 3p lone pair orbitals of the C 5 H 4 NS - ligand and the cooperativity between An-N and An-S bonds that provides additional stability for the transuranic elements.