Delivery of a Masked Uranium(II) by an Oxide-Bridged Diuranium(III) Complex.

Oxide is an attractive linker for building polymetallic complexes that provide molecular models for metal oxide activity, but studies of these systems are limited to metals in high oxidation states. Herein, we synthesized and characterized the molecular and electronic structure of diuranium bridged UIII /UIV and UIII /UIII complexes. Reactivity studies of these complexes revealed that the U-O bond is easily broken upon addition of N-heterocycles resulting in the delivery of a formal equivalent of UIII and UII , respectively, along with the uranium(IV) terminal-oxo coproduct. In particular, the UIII /UIII oxide complex effects the reductive coupling of pyridine and two-electron reduction of 4,4'-bipyridine affording unique examples of diuranium(III) complexes bridged by N-heterocyclic redox-active ligands. These results provide insight into the chemistry of low oxidation state metal oxides and demonstrate the use of oxo-bridged UIII /UIII complexes as a strategy to explore UII reactivity.