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 LArUI(DME) ((LAr)2-= 2,2”-bis(Dippanilide)-p-terphenyl; Dipp = 2,6-diisopropylphenyl) with LiNImDipp ((NImDipp)= 1,3-bis(Dipp)-imidaozolin-2-iminato) generates the sterically congested 3N-coordinate compound LArU(NImDipp) (1). Complex 1reacts with 1 equiv of Ph3CN3to give the U(IV) azide LArU(N3)(NImDipp) (2). Structural analysis of 2reveals inequivalent Nα-Nβ> Nβ-Nγdistances indicative of an activated azide moiety predisposed to N2loss. Room-temperature photolysis of benzene solutions of 2affords the U(IV) amide (N-LAr)U(NImDipp) (3) via intramolecular N-atom insertion into the benzylic C-H bond of a pendant isopropyl group of the (LAr)2- ligand. The formation of 3occurs as a result of the intramolecular interception of the intermediately generated, terminal uranium nitride (LAr)U(N)(NImDipp) (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 (LAr)U[NCN(C6H3Me2)](NImDipp) (5) and (N,C-LAr*)U(N=PMe3)(NImDipp) (6), respectively. These results expand upon the limited reactivity studies of terminal uranium-nitride moieties and provide new insights into their chemical properties.