Synthesis of Terminal Monochalcogenide and Dichalcogenide Complexes of Uranium Using Polychalcogenides, [En]2- (E = Te, n=2; E = Se, n=4), as Chalcogen Atom Transfer Reagents

Reaction of KH with elemental tellurium, in the presence of 18-crown-6, results in the formation of the ditelluride, [K(18-crown-6)](2)[Te-2] (1), in good yield. Similarly, reaction of KH with elemental selenium, in the presence of 18-crown-6, results in the formation of [K(18-crown-6)](2)[Se-4] (4). Both 1 and 4 are capable of chalcogen atom transfer to U(III). For example, addition of 0.5 equiv or 1 equiv of [K(18-crown-6)](2)[Te-2] (1) to [U(NR2)(3)] (R = SiMe3) or [U(I)(NR2)(3)], respectively, results in the formation of the new U(IV) tellurides, [K(18-crown-6)][U(Te)(NR2)(3)] (2), and [K(18-crown-6)][U(eta(2)-Te-2)(NR2)(3)] (3), in moderate yields, while addition of 0.5 equiv of [K(18-crown-6)](2)[Se-4] (4) to [U(NR2)3] results in the formation of the U(IV) diselenide, [K(18-crown-6)][U(eta(2)-Se-2)(NR2)(3)] (5). Interestingly, 5 can be converted into the monoselenide [K(18-crown-6)][U(Se)(NR2)(3)] (6) via reaction with Ph3P.