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The addition of 4.5 equiv of LiCH(2)SiMe(3) to [Li(THF)](2)[U(O(t)Bu)(6)], in the presence of LiCl, results in the formation of the homoleptic uranium(IV) alkyl complex [Li(14)(O(t)Bu)(12)Cl][U(CH(2)SiMe(3))(5)] (1) in low yield. Complex 1 has been characterized by X-ray crystallography. As a solid, 1 is thermally stable for several days at room temperature. However, 1 rapidly decomposes in C(6)D(6), as indicated by (1)H and (7)Li{(1)H} NMR spectroscopy, owing to the lability of the [Li(14)(O(t)Bu)(12)Cl](+) cation. To avoid the formation of the [Li(14)(O(t)Bu)(12)Cl](+) counterion, alkylation of UCl(4) was investigated. Treatment of UCl(4) with 5 equiv of LiCH(2)SiMe(3) or LiCH(2)(t)Bu at -25 degrees C in THF/Et(2)O affords [Li(DME)(3)][U(CH(2)SiMe(3))(5)] (2) and [Li(THF)(4)][U(CH(2)(t)Bu)(5)] (3), respectively, in good yields. Similarly, treatment of UCl(4) with 6 equiv of MeLi or KCH(2)C(6)H(5) generates the U(IV) hexa(alkyl) complexes [Li(TMEDA)](2)[UMe(6)] (4) and {[K(THF)](3)[K(THF)(2)][U(CH(2)C(6)H(5))(6)](2)}(x) (5) in 38% and 70% yields, respectively. The structures of 3-5 have been confirmed by X-ray crystallography. Complexes 2, 3, and 5 are thermally stable solids which can be stored at room temperature for several days, whereas 4 decomposes upon warming above -25 degrees C. The electronic and magnetic properties of 2, 3, and 5 were also investigated by NIR spectroscopy and SQUID magnetometry.

Addition of 1 equiv of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) to U(NR(2))(3) in hexanes affords U(O)(NR(2))(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 Me(3)NO to U(NR(2))(3) (R = SiMe(3)) in pentane generates the U(IV) bridging oxo [(NR(2))(3)U](2)(μ-O) (3) in moderate yields. Also formed in this reaction, in low yield, is the U(IV) iodide complex U(I)(NR(2))(3) (4). The iodide ligand in 4 likely originates from residual NaI, present in the U(NR(2))(3) starting material. Complex 4 can be generated rationally by addition of 0.5 equiv of I(2) to a hexane solution of U(NR(2))(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.

A rare, low-spin Fe(IV)  imide complex [(pyrr2py)Fe=NAd] (pyrr2 py(2-) = bis(pyrrolyl)pyridine; Ad = 1-adamantyl) confined to a cis-divacant octahedral geometry, was prepared by reduction of N3Ad by the Fe(II)  precursor [(pyrr2py)Fe(OEt2)]. The imide complex is low-spin with temperature-independent paramagnetism. In comparison to an authentic Fe(III) complex, such as [(pyrr2py)FeCl], the pyrr2py(2-) ligand is virtually redox innocent.