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

Removal of chloride from CoCl2 with TlPF6 in acetonitrile, followed by addition of excess nitrosobenzene, yielded the eight-coordinate cobalt­(II) complex salt [Co­{Ph­(O)­NN­(O)­Ph}4]­(PF6)2, shown by single-crystal X-ray analysis to have a distorted tetragonal geometry. The analogous treatment of the bipyridyl complex Co­(bpy)­Cl2 yielded the mixed-ligand cobalt­(II) complex salt [Co­(bpy)­{Ph­(O)­NN­(O)­Ph}2]­(PF6)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]­(FeCl4)2. The use of TlPF6 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 PF6– counteranion. Coordination number appears to be more important than d electron count in determining the geometry and metal–ligand bond distances of diphenylazodioxide complexes.