Synthesis, Molecular and Electronic Structure of UV(O)[N(SiMe3)2]3

Addition of 1 equiv of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) to U(NR2)(3) in hexanes affords U(O)(NR2)(3) (2), which can be isolated in 73% yield. Complex 2 is a rare example of a terminal U(V) oxo complex. In contrast, addition of 1 equiv of Me3NO to U(NR2)(3) (R = SiMe3) in pentane generates the U(IV) bridging oxo [(NR2)(3)U](2)(mu-O) (3) in moderate yields. Also formed in this reaction, in low yield, is the U(IV) iodide complex U(I)(NR2)(3) (4). The iodide ligand in 4 likely originates from residual NaI, present in the U(NR2)(3) starting material. Complex 4 can be generated rationally by addition of 0.5 equiv of I-2 to a hexane solution of U(NR2)(3), where it can be isolated in moderate yield as a tan crystalline solid. The solid-state molecular structures and magnetic susceptibilities of 2, 3, and 4 have been measured. In addition, the electronic structures of 2 and 3 have been investigated by density functional theory (DFT) methods.