Monoimido derivatives of uranium(IV) have been prepared by both metathesis and direct protonation routes. The reaction of lithium anilide with (eta(5)-C(5)Me(5))(2)UMeCl in the presence of tetramethylethylenediamine (TMED) results in the isolation of the salt [Li(TMED)][eta(5)-C(5)Me(5))(2)U(NC6H5)Cl] (1). Compound 1 crystallizes in the space group P3(2), with unit cell dimensions a = 17.545(2) Angstrom, c = 9.407(2) Angstrom, V = 2507.8(7) Angstrom(3), Z = 3. Metathesis reactions with potassium anilide salts similarly result in the formation of monoimido chloride anionic derivatives of U(IV); these can be converted to neutral base adducts by reaction with the appropriate Lewis base at room temperature. A more direct route to the formation of neutral organoimido species with sterically encumbered aryl substituents is the reaction of (eta(5)-C(5)Me(5))(2)UMe(2) with 1 equiv H2NAr (Ar = 2,6-diisopropylphenyl or 2,4,6-tri-tert-butylphenyl). The base-free 2,6-diisopropyl derivative is highly soluble in all solvents, and the product of this protonation is best isolated as a base adduct, (eta(5)-C(5)Me(5))(2)U(N-2,6-i-Pr2C6H3)(THF) (6). The 2,4,6-tri-tert-butylphenylaniline product does not react further with tetrahydrofuran, however, and may be isolated as the base-free imido complex (eta(5)-C-5-Me(5))(2)U(N-2,4,6-t-Bu(3)C(6)H(2)) (8) Compound 8 crystallizes in the space group Pmn2(1), with unit cell dimensions a = 13.450(5) Angstrom, b = 12.138(5) Angstrom, c = 10.510(3) Angstrom, V = 1715.9(10) Angstrom(3), Z = 2. All of the organoimido compounds of uranium(IV) exhibit rich chemistry with two electron oxidative atom transfer reagents, providing an entirely new class of organouranium(VI) complexes containing terminal imido and oxo functional groups. Bis(imido) complexes such as (eta(5)-C(5)M(5))(2)U(NC6H5)(2) (3) can also be prepared by the unprecedented intramolecular reductive cleavage of 1,2-diphenylhydrazine at a uranium(IV) center. These complexes are in general surprisingly unreactive, but compound 3 will effect the unprecedented homolytic cleavage of dihydrogen to yield a bis(amide) derivative. The physical properties and chemical stability of these species suggests that significant uranium-imido and -oxo multiple bond character is present.