A Structural and Theoretical Investigation of Equatorial cis and trans Uranyl Phosphinimine and Uranyl Phosphine Oxide Complexes UO₂Cl₂(Cy₃PNH)₂ and UO₂Cl₂(Cy₃PO)₂

Phosphinimine ligands (Cy₃PNH) readily react with UO₂Cl₂(THF)₃ (THF = tetrahydrofuran) to give UO₂Cl₂(Cy₃PNH)₂, which contains strong U−N interactions and exists as cis and trans isomers in the solid and solution state. Solution NMR experiments and computational analysis both support the trans form as the major isomer in solution, although the cis isomer becomes more stabilized with an increase in the dielectric constant of the solvent. Mayer bond orders, energy decomposition analysis, and examination of the molecular orbitals and total electron densities support a more covalent bonding interaction in the U−NHPCy₃ bond compared with the analogous bond of the related U−OPCy₃ compounds.