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-g, Se, Te) to U(H2C=PPh3)(NR2)(3) (R = SiMe3) (1) in Et2O results in generation of the terminal chalcogenide complexes, [Ph3PCH3][U(E)(NR2)(3)] (E = S, 2; Se, 3; Te, 4; R = SiMe3), in modest yield. Complexes 2-4 represent extremely rare examples of terminal uranium monochalcogenides. Synthesis of the oxo analogue, [Cp*Co-2][U(O)(NR2)(3)] (5), was achieved by reduction of [U(O)(NR2)(3)] with Cp*2CO. 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.