Synthesis and Characterization of Cobalt(II) N,N′-Diphenylazodioxide Complexes

[Image: see text] Removal of chloride from CoCl(2) with TlPF(6) in acetonitrile, followed by addition of excess nitrosobenzene, yielded the eight-coordinate cobalt(II) complex salt [Co{Ph(O)NN(O)Ph}(4)](PF(6))(2), shown by single-crystal X-ray analysis to have a distorted tetragonal geometry. The analogous treatment of the bipyridyl complex Co(bpy)Cl(2) yielded the mixed-ligand cobalt(II) complex salt [Co(bpy){Ph(O)NN(O)Ph}(2)](PF(6))(2), whose single-crystal X-ray structure displays a trigonal prismatic geometry, similar to that of the iron(II) cation in the previously known complex salt [Fe{Ph(O)NN(O)Ph}(3)](FeCl(4))(2). The use of TlPF(6) to generate solvated metal complex cations from chloride salts or chlorido complexes, followed by the addition of nitrosobenzene, is shown to be a useful synthetic strategy for the preparation of azodioxide complex cations with the noncoordinating, diamagnetic PF(6)(–) counteranion. Coordination number appears to be more important than d electron count in determining the geometry and metal–ligand bond distances of diphenylazodioxide complexes.