Reduction of pentavalent uranyl to U(IV) facilitated by oxo functionalization.

Addition of 2 equiv of B(C(6)F(5))(3) to [Cp*(2)Co][U(V)O(2)((Ar)acnac)(2)] (1) [(Ar)acnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-(t)Bu(2)C(6)H(3)] results in the formation of [Cp*(2)Co][U(V){OB(C(6)F(5))(3)}(2)((Ar)acnac)(2)] (2) in good yield. Reduction of 2 with 1 equiv of Cp*(2)Co generates [Cp*(2)Co](2)[U(IV){OB(C(6)F(5))(3)}(2)((Ar)acnac)(2)] (3), also in good yield. This reaction is chemically reversible, as shown by the reaction of 3 with AgOTf, which regenerates 2. Interestingly, addition of only 1 equiv of B(C(6)F(5))(3) to 1 does not produce the monofunctionalized U(V) complex. Instead, the products of disproportionation, namely, 3 and U(VI)O(2)((Ar)acnac)(2), are observed in a 1:1 ratio.