For 30 years, it has been known that the bent, bis(imido) uranium complexes, Cp*2U(NAr)2, have proton NMR spectra in which the aryl protons display unusual chemical shifts that range from ~1 to 9 ppm despite the diamagnetism that is expected from their 5f06d0 valence electron configurations. These unusual chemical shifts have been attributed to temperature independent paramagnetism (TIP). We have begun to further explore this phenomenon through the synthesis of a family of Cp2U(NR)2 derivatives in which the Cp group and R group are varied. Computational results show that these molecules have a low-lying triplet excited state that is likely responsible for the unusual NMR spectra as well as a low-energy absorption in their UV-Vis-NIR spectra. These results will be discussed along with the reactivty of these unusual molecules.

Cp2U(Imido)2 complexes: Simple molecules with complex electronic structures

ACS Spring 2022

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