Synthesis and structural characterization of mono- and bimetallic azodioxide complexes of first-series transition metals

The treatment of metal chlorides MCl₂ or metal chlorido complexes M(bpy)Cl₂ (M = Mn, Ni, Cu, bpy = 2,2′-bipyridyl) with TlPF₆ in acetonitrile to precipitate TlCl, followed by addition of excess nitrosobenzene, yielded monometallic or bimetallic azodioxide complex salts of the form [M(az)₄](PF₆)₂, [M(bpy)₂(az)](PF₆)₂, and [{M(bpy)(az)(μ-Cl)}₂](PF₆)₂ (az = cis-N,N′-diphenylazodioxide), which have been structurally characterized via single-crystal X-ray diffraction. The method of activation of chloride salts or chlorido complexes by chloride abstraction with Tl⁺, followed by the addition of nitrosobenzene, continues to be an effective strategy for the synthesis of azodioxide complexes, and it has enabled the synthesis of the first structurally characterized azodioxide complexes of any metals of Groups 7, 10, or 11.