Low- and Mid-Valent Uranium Species Supported by Phenyltris(oxazolinyl)borate Ligands

Abstract

The synthesis and characterization of a family of uranium derivatives featuring the phenyltris(4,4-dimethyl-2-oxazolinyl)borate (ToM) ligand framework was achieved. Uranium(IV) halide compounds, specifically ToMUCl3(THF) and ToMUI3, were generated by adding 1 equiv of Tl[ToM] to either UCl4 or UI3(THF)4, respectively. The tetravalent derivatives ToMUCl2(NPh2) and ToMUI(═N-Ad)(THF) were also synthesized, showing that ToM supports uranium amido and imido species. Attempts to make bis(phenyltris(oxazolinyl)borate) compounds were unsuccessful. However, when the smaller hydrotris(pyrazolyl)borate (Tp) ligand was used, a mixed bis(ligand) derivative, TpToMUI, was isolated. All of the compounds were characterized by 1H NMR, infrared, and electronic absorption spectroscopies. Where possible, X-ray crystallography was used to assess structural parameters.