title: Preparation and reactivity of the versatile uranium(IV) imido complexes U(NAr)Cl₂(R₂bpy)₂ (R = Me, (t)Bu) and U(NAr)Cl₂(tppo)₃.
abstract: Uranium tetrachloride undergoes facile reactions with 4,4'-dialkyl-2,2'-bipyridine, resulting in the generation of UCl4(R2bpy)2, R = Me, (t)Bu. These precursors, as well as the known UCl4(tppo)2 (tppo = triphenylphosphine oxide), react with 2 equiv of lithium 2,6-di-isopropylphenylamide to provide the versatile uranium(IV) imido complexes, U(NDipp)Cl2(L)n (L = R2bpy, n = 2; L = tppo, n = 3). Interestingly, U(NDipp)Cl2(R2bpy)2 can be used to generate the uranium(V) and uranium(VI) bisimido compounds, U(NDipp)2X(R2bpy)2, X = Cl, Br, I, and U(NDipp)2I2((t)Bu2bpy), which establishes these uranium(IV) precursors as potential intermediates in the syntheses of high-valent bis(imido) complexes from UCl4. The monoimido species also react with 4-methylmorpholine-N-oxide to yield uranium(VI) oxo-imido products, U(NDipp)(O)Cl2(L)n (L = (t)Bu2bpy, n = 1; L = tppo, n = 2). The aforementioned molecules have been characterized by a combination of NMR spectroscopy, X-ray crystallography, and elemental analysis. The chemical reactivity studies presented herein demonstrate that Lewis base adducts of uranium tetrachloride function as excellent sources of U(IV), U(V), and U(VI) imido species.
authors.affiliation: MPA Division, Los Alamos National Laboratory , MS J514, Los Alamos, New Mexico 87545, United States.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Jilek
authors.forename: Neil C
authors.initials: NC
authors.lastname: Tomson
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Shook
authors.forename: Brian L
authors.initials: BL
authors.lastname: Scott
authors.forename: James M
authors.initials: JM
authors.lastname: Boncella