[U(bipy)₄]: A Mistaken Case of U⁰?

Abstract

After more than 50 years, the synthesis and electronic structure of the first and only reported "U⁰ complex" [U(bipy)₄ ] (1) has been reinvestigated. Additionally, its one-electron reduced product [Na(THF)₆ ][U(bipy)₄ ] (2) has been newly discovered. High resolution crystallographic analyses combined with magnetic and computational data show that 1 and its derivative 2 are best described as highly reduced species containing mid-to-high-valent uranium ligated by redox non-innocent ligands.