Activation of Gas-Phase Uranyl: From an Oxo to a Nitrido Complex

The uranyl moiety, UO₂²⁺, is ubiquitous in the chemistry of uranium, the most prevalent actinide. Replacing the strong uranium–oxygen bonds in uranyl with other ligands is very challenging, having met with only limited success. We report here uranyl oxo bond activation in the gas phase to form a terminal nitrido complex, a previously elusive transformation. Collision induced dissociation of gas-phase UO₂(NCO)­Cl₂^– in an ion trap produced the nitrido oxo complex, NUOCl₂^–, and CO₂. NUOCl₂^– was computed by DFT to have <i>C_s</i> symmetry and a singlet ground state. The computed bond length and order indicate a triple U–N bond. Endothermic activation of UO₂(NCO)­Cl₂^– to produce NUOCl₂^– and neutral CO₂ was computed to be thermodynamically more favorable than NCO ligand loss. Complete reaction pathways for the CO₂ elimination process were computed at the DFT level