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[Te2] (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[Se4] (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[Te2] (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(η2-Te2)­(NR2)3] (3), in moderate yields, while addition of 0.5 equiv of [K­(18-crown-6)]2­[Se4] (4) to [U­(NR2)3] results in the formation of the U­(IV) diselenide, [K­(18-crown-6)]­[U­(η2-Se2)­(NR2)3] (5). Interestingly, 5 can be converted into the monoselenide [K­(18-crown-6)]­[U­(Se)­(NR2)3] (6) via reaction with Ph3P.