Reduction of Carbonyl Groups by Uranium(III) and Formation of a Stable Amide Radical Anion

Methyl benzoate, N, N-dimethylbenzamide, and benzophenone were reduced by U-III[N(SiMe3)(2)](3) resulting in uranium(IV) products. Reduction of benzophenone lead to U-IV[OC center dot Ph-2)][N(SiMe3)(2)](3), (1.1) which forms the dinuclear complex, [N(SiMe3)(2)](3)U-IV(OCPhPh-CPh2O) U-IV[N(SiMe3)(2)](3) (1.2), through coupling of the ketyl radical species upon crystallization. Reaction of N, N-dimethylbenzamide with U-III[N(SiMe3)(2)](3) resulted in U-IV[OC center dot(Ph)(NMe2)][N(SiMe3)(2)](3) (2), a uranium(IV) compound and the first example of a chargeseparated amide radical. In the case of methyl benzoate, the reduction resulted in U-IV(OMe)[N(SiMe3)(2)](3) (3) and benzalde-hyde as the reduced organic fragment. Compound 2 showed the ability to act as a uranium(III) synthon in its reactivity with trimethylsilyl azide, a reaction that yielded U-V(=NSiMe3)[N(SiMe3)(2)](3). Additionally, 2 was reduced with potassium graphite resulting in [U(mu-O)[O= C(NMe2)(Ph)] [N(SiMe3)(2)](2)](2) (4), a dinuclear uranium compound bridged by oxo ligands. Reduction of 2 in the presence of 15-crown-5 afforded isolation of the mono-oxo compound, [(15-crown-5) K-2][UO[N(SiMe3)2](3)] (5). The results expand the reduction capabilities of UIII complexes and demonstrate a strategy for isolating novel metal-stabilized radicals.