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)-imidazolin-2-iminato) generates the sterically congested 3N-coordinate compound LArU(NImDipp) (1). Complex 1 reacts with 1 equiv. of Ph3CN3 to give the U(iv) azide LArU(N3)(NImDipp) (2). Structural analysis of 2 reveals inequivalent Nα-Nβ > Nβ-Nγ distances indicative of an activated azide moiety predisposed to N2 loss. Room-temperature photolysis of benzene solutions of 2 affords 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 3 occurs 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 2 in the presence of an isocyanide or PMe3 to give (LAr)U[NCN(C6H3Me2)](NImDipp) (5) and (N,C-LAr*)U(N[double bond, length as m-dash]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.