Exceptional Uranium-Nitride Triple Bond Covalency confirmed with NMR

The Liddle group continues to deeply probe the unusual nature of the actinide-main group bonds through combined experimental and computational studies. We previously highlighted the first U-N triple bonds along with a number of other novel 5f-block complexes.

In a recent Nature Communications paper, the Liddle group manages to obtain the solid state NMR spectrum of a 15N labeled U(VI)-nitride complex. DFT calculations with ADF helped to understand the extremely large upfield shift and anisotropy through a detailed NLMO analysis of the diamagnetic, paramagnetic, and spin-orbit contributions to the NMR tensor (see tutorial).

The large isotropic chemical shift is found to come from the field-induced mixing of the UN σ/π* and π/σ* orbitals. A strong correlation between the Mayer bond order and deshielding is found, further corroborating the previous assertions that the U(VI)-N bond is strongly covalent.

J. Du et al., Exceptional uranium(VI)-nitride triple bond covalency from 15N nuclear magnetic resonance spectroscopy and quantum chemical analysis, Nature Communications, 12, 5649 (2021)
See also: Blog post ‘behind the article’

Key concepts