A complete family of terminal uranium chalcogenides, [U(E)(N{SiMe3}2)3]- (E = O, S, Se, Te).

Addition of 1 equiv of E (E = 0.125 S(8), Se, Te) to U(H(2)C═PPh(3))(NR(2))(3) (R = SiMe(3)) (1) in Et(2)O results in generation of the terminal chalcogenide complexes, [Ph(3)PCH(3)][U(E)(NR(2))(3)] (E = S, 2; Se, 3; Te, 4; R = SiMe(3)), in modest yield. Complexes 2-4 represent extremely rare examples of terminal uranium monochalcogenides. Synthesis of the oxo analogue, [Cp*(2)Co][U(O)(NR(2))(3)] (5), was achieved by reduction of [U(O)(NR(2))(3)] with Cp*(2)Co. All complexes were fully characterized, including analysis by X-ray crystallography. In the solid state, complexes 2-5 feature short U-E bond lengths, suggestive of actinide-ligand multiple bonding.