Intra- and Intermolecular Interception of a Photochemically Generated Terminal Uranium Nitride

The photochemically generated synthesis of a terminal uranium nitride species is here reported and an examination of its intra- and intermolecular chemistry is presented. Treatment of the U(III) complex L^ArUI(DME) ((L^Ar)^2-= 2,2”-bis(Dippanilide)-p-terphenyl; Dipp = 2,6-diisopropylphenyl) with LiNIm^Dipp ((NIm^Dipp)^–= 1,3-bis(Dipp)-imidaozolin-2-iminato) generates the sterically congested 3N-coordinate compound L^ArU(NIm^Dipp) (1). Complex 1reacts with 1 equiv of Ph₃CN₃to give the U(IV) azide L^ArU(N₃)(NIm^Dipp) (2). Structural analysis of 2reveals inequivalent N_α-N_β> N_β-N_γdistances indicative of an activated azide moiety predisposed to N₂loss. Room-temperature photolysis of benzene solutions of 2affords the U(IV) amide (N-L^Ar)U(NIm^Dipp) (3) via intramolecular N-atom insertion into the benzylic C-H bond of a pendant isopropyl group of the (L^Ar)^2- ligand. The formation of 3occurs as a result of the intramolecular interception of the intermediately generated, terminal uranium nitride (L^Ar)U(N)(NIm^Dipp) (3’). Evidence for the formation of 3’is further bolstered by its intermolecular capture, accomplished by photolyzing solutions of 2in the presence of an isocyanide or PMe₃to give (L^Ar)U[NCN(C₆H₃Me₂)](NIm^Dipp) (5) and (N,C-L^Ar*)U(N=PMe₃)(NIm^Dipp) (6), respectively. These results expand upon the limited reactivity studies of terminal uranium-nitride moieties and provide new insights into their chemical properties.