Co(II) complexes of aminotrisphenolate ((ArO)3N(3-)) ligands can be prepared straightforwardly in high yield. X-ray analysis reveals these complexes to comprise of two different hemispheres, one containing an anionic Co((ArO)3N)(-) and the other a cationic (ArO)3NH(+) unit, which are associated through hydrogen bonding. These Co(II) complexes can be easily converted into their Co(III) analogues in air in the presence of suitable bases such as dimethylaminopyridine and 2,2'-bipyridine, and the structural features and magnetic properties of these latter compounds are also reported.