Addition of 2 equiv of HSiEt3 to UO2((Ar)acnac)(2) ((Ar)acnac = ArNC(Ph)CHC(Ph)O, Ar = 3,5-(Bu2C6H3)-Bu-t) in the presence of 1 equiv of B(C6F5)(3) results in formation of the U(V) bis(silyloxide) complex [U(OSiEt3)(2)((Ar)acnac)(2)][HB-(C6F5)(3)] (1) in 80% yield. Also produced in the reaction, as a minor product, is U(OSiEt3)(OB{C6F5}(3))((Ar)acnac)(2) (2). Interestingly, thermolysis of 1 at 85 degrees C for 24 h also results in formation of 2, concomitant with production of Et3SiH. Addition of 1 equiv of Cp2Co to 1 results in formation of U(OSiEt3)(2)((Ar)acnac)(2) (3) and [Cp2Co][HB(C6F5)(3)] (4), which can be isolated in 61% and 71% yields, respectively. Complexes 1-3 have been characterized by X-ray crystallography, while the solution-phase redox properties of 1 have been measured with cyclic voltammetry.