C-H Bond Addition across a Transient Uranium-Nitrido Moiety and Formation of a Parent Uranium Imido Complex

Abstract

Uranium complexes in the +3 and +4 oxidation states were prepared using the anionic PN^- (PN^- = ( N-(2-(diisopropylphosphino)-4-methylphenyl)-2,4,6-trimethylanilide) ligand framework. New complexes include the halide starting materials, (PN)₂U^IIII (1) and (PN)₂U^IVCl₂ (2), which both yield (PN)₂U^IV(N₃)₂ (3) by reaction with NaN₃. Compound 3 was reduced with potassium graphite to produce a putative, transient uranium-nitrido moiety that underwent an intramolecular C-H activation to form a rare example of a parent imido complex, [K(THF)₃][(PN)U^IV(═NH)[ ⁱPr₂P(C₆H₃Me)N(C₆H₂Me₂CH₂)]] (4). Calculated reaction energy profiles strongly suggest that a C-H insertion becomes unfavorable when a reductant is present, offering a distinctively different reaction pathway than previously observed for other uranium nitride complexes.