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 [N(SiMe ) ] resulting in uranium(IV) products. Reduction of benzophenone lead to U [OC⋅Ph )][N(SiMe ) ] , (1.1) which forms the dinuclear complex, [N(SiMe ) ] U (OCPhPh-CPh O)U [N(SiMe ) ] (1.2), through coupling of the ketyl radical species upon crystallization. Reaction of N,N-dimethylbenzamide with U [N(SiMe ) ] resulted in U [OC⋅(Ph)(NMe )][N(SiMe ) ] (2), a uranium(IV) compound and the first example of a charge-separated amide radical. In the case of methyl benzoate, the reduction resulted in U (OMe)[N(SiMe ) ] (3) and benzaldehyde 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 (=NSiMe )[N(SiMe ) ] . Additionally, 2 was reduced with potassium graphite resulting in [U(μ-O)[O=C(NMe )(Ph)][N(SiMe ) ] ] (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][UO[N(SiMe ) ] ] (5). The results expand the reduction capabilities of U complexes and demonstrate a strategy for isolating novel metal-stabilized radicals.