Two uranium(VI) uranyl compounds, Cp*UO2((PDIMe)-P-Mes) (3) and Cp*UO2(Bu-t-(PDIMe)-P-Mes) (3-Bu-t) (Cp* = 1,2,3,4,5-pentamethylcyclopentadienide; (PDIMe)-P-Mes = 2,6-((Mes)N=CMe)(2)C5H3N; Bu-t-(PDIMe)-P-Mes = 2,6-((Mes)-N=CMe)(2)-p-C(CH3)(3)C5H2N; Mes = 2,4,6-trimethylphenyl), have been synthesized by addition of N-methylmorpholine N-oxide to trianionic pyridine(diimine) uranium(IV) precursors, Cp*U((PDIMe)-P-Mes)(THF) (1), Cp*U((PDIMe)-P-Mes)(HMPA) (1-HMPA), and Cp*U(Bu-t-(PDIMe)-P-Mes)(THF) (1-Bu-t). These uranyl complexes contain singly reduced pyridine(diimine) ligands suggesting formation occurs via cooperative figand/metal oxidation. Treating 3 or 3-Bu-t with stoichiometric equivalents of Me3SiI results in stepwise oxo silylation to form (Me3SiO)(2)UI2((PDIMe)-P-Mes) (5) or (Me3SiO)UI2(Bu-t-(PDIMe)-P-Mes) (5-Bu-t), respectively. Additional equivalents result in uranium-oxo bond scission and formation of UI4(1,4-dioxane)(2) with extrusion of hexamethyldisiloxane. The uranium complexes have been characterized via multinuclear NMR, vibrational, and electronic absorption spectroscopies and, in some cases, X-ray crystallography.