A General and Modular Synthesis of Monoimidouranium(IV) Dihalides

The conproportionation reaction between the dimeric diimidouranium(V) species [U((NBu)-Bu-t)(2)(I)(Bu-t(2)-bpy)](2) ((t)Bu(2)bpy = 4,4'-di-tert-butyl-2,2'-bipyridyl) and UI3(THF)(4) in the presence of additional (t)Bu(2)bpy yields U((NBu)-Bu-t)(I)(2)((t)Bu(2)bPy)(THF)(2) (2), an unprecedented example of a monoimidouranium(IV) dihalide complex. The general synthesis of this family of uranium(IV) derivatives can be achieved more readily by adding 2 equiv of MN(H)R (M = Li, K; R = Bu-t, 2,6-(PrC6H3)-Pr-i, 2-(BuC6H4)-Bu-t) to UX4 in the presence of coordinating Lewis bases to give complexes with the general formula U(NR)(X)(2)(L)(n) (X = Cl, I; L = (t)Bu(2)bpy, n = 1; L = THF, n = 2). The complexes were characterized by H-1 NMR spectroscopy and single-crystal X-ray diffraction analysis of compounds 2 and {U[N(2,6-(PrC6H3)-Pr-i)] (Cl)(2)-(THF)(2)}2 (4). (The X-ray structures of 5 and 6 are reported in the Supporting Information.)