Facile Reductive Silylation of UO₂²⁺ to Uranium(IV) Chloride

General reductive silylation of the UO₂²⁺ cation occurs readily in a one-pot, two-step stoichiometric reaction at room temperature to form uranium(IV) siloxides. Addition of two equivalents of an alkylating reagent to UO₂ X₂ (L)₂ (X=Cl, Br, I, OTf; L=triphenylphosphine oxide, 2,2'-bipyridyl) followed by two equivalents of a silyl (pseudo)halide, R₃ Si-X (R=aryl, alkyl, H; X=Cl, Br, I, OTf, SPh), cleanly affords (R₃ SiO)₂ UX₂ (L)₂ in high yields. Support is included for the key step in the process, reduction of U^VI to U^V . This procedure is applicable to a wide range of commercially available uranyl salts, silyl halides, and alkylating reagents. Under this protocol, one equivalent of SiCl₄ or two equivalents of Me₂ SiCl₂ results in direct conversion of the uranyl to uranium(IV) tetrachloride. Full spectroscopic and structural characterization of the siloxide products is reported.