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 Ar UI(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 3 N -coordinate compound L Ar U(NIm Dipp ) ( 1 ). Complex 1 reacts with 1 equiv of Ph 3 CN 3 to give the U(IV) azide L Ar U(N 3 )(NIm Dipp ) ( 2 ). Structural analysis of 2 reveals inequivalent N α -N β > N β -N γ distances indicative of an activated azide moiety predisposed to N 2 loss. Room-temperature photolysis of benzene solutions of 2 affords 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 3 occurs 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 2 in the presence of an isocyanide or PMe 3 to give (L Ar )U[NCN(C 6 H 3 Me 2 )](NIm Dipp ) ( 5 ) and ( N , C -L Ar *)U(N=PMe 3 )(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.