Reaction of [U{(SiMe₂NPh)₃-tacn}Cl] with LiNEt₂ or LiNPh₂ affords the corresponding amide compounds, [U{(SiMe₂NPh)₃-tacn}(NR₂)] (R = Et (1), R = Ph (2)). The complexes have been fully characterized by spectroscopic methods and the solid-state structure of 1 was determined by single-crystal X-ray diffraction analysis. The six nitrogen atoms of the tris(dimethylsilylanilide)triazacyclononane ligand are in a trigonal prismatic configuration with the nitrogen atom of the diethylamide ligand capping one of the trigonal faces of the trigonal prism. Crystallization of 2 from CH₃CN solution gave crystals of the six-membered heterocycle [U{(SiMe₂NPh)₃-tacn}{κ²-(HNC(Me))₂CCN}] (3). The reactivity of the amides was investigated. Both compounds undergo acid–base reactions with protic substrates such as HOC₆H₂-2,4,6-Me₃, 3,5-Me₂pzH (pz = pyrazolyl) and HSC₅H₄N to give the corresponding [U{(SiMe₂NPh)₃-tacn}X] (X = OC₆H₂-2,4,6-Me₃ (4), 3,5-Me₂pzH (5), κ²-SC₅H₄N (6)) complexes. The solid-state structures of 3 and 6 were determined by single-crystal X-ray diffraction and revealed that the compounds are eight-coordinate with dodecahedral geometry.