Synthesis, structure and physical characterization of the dimer {[(bpy)2Co]2(TPOA)}4+ (bpy = 2,2′-dipyridyl; H2TPOA = N,N′,N′′,N′′′-tetraphenyl oxalamidine)

The reaction between CoCl2, 2,2′-dipyridyl (bpy) and N,N′,N′′,N′′′-tetraphenyl oxalamidine (H2TPOA) in a water/ethanol mixture yields the {[(bpy)2Co]2(TPOA)}2+ dimer, that is immediately oxidized in aerobic conditions leading to the CoIII species {[(bpy)2Co]2(TPOA)}4+. This cation was isolated as the {[(bpy)2Co]2(TPOA)}(PF6)4 (1) salt, that was characterized by X-ray diffraction on single crystals. The dimer is formed by two CoIII ions in octahedral coordination bridged by a deprotonated μ2-TPOA ligand. The CoIII ions appear in its low spin configuration. Thus, the dimers are essentially diamagnetic, as shown by 1H NMR and magnetic measurements.