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

• Published in: Inorganic chemistry Vol. 53; no. 18; pp. 9818 - 9826
• Main Authors: Jilek, Robert E, Tomson, Neil C, Shook, Ryan L, Scott, Brian L, Boncella, James M
• Format: Journal Article
• Language: English
• Published: American Chemical Society 15-09-2014
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic5014208

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.