Addition of 0.5 equiv of NaN3 to U[NR2](3) (R = SiMe3) affords the metallacycle [Na(DME)(2)(TMEDA)][(NR2)(2)U(mu-N)(CH2SiMe2NR)U(NR2)(2)] (1) in 69% yield. Complex 1 is readily oxidized by 0.5 equiv of I-2, generating the mixed valent U(IV/V) nitrido complex (NR2)(2)U(mu-N)(CH2SiMe2NR)U(NR2)(2) (2). Alternatively, oxidation of 1 with 1 equiv of Me3NO affords the oxo-nitrido complex [Na(DME)(2)][(NR2)(2)(O)U(mu-N)(CH2SiMe2NR)U(NR2)(2)] (3) in good yield. The solid-state molecular structures of 1-3 have been determined by X-ray crystallography. A notable feature of these complexes are the inequivalent U=N-U bonding interactions. Moreover, 3 contains a trans oxo-nitrido [O=U=N](+) moiety with metrical parameters approximating those of the uranyl cation, UO22+. The magnetic properties of 1-3 were investigated by SQUID magnetometry.