dibenzo[e,n][1,4,8,12]tetraazacyclopentaadecine [H 2 (3,2 mac)], i.e. M(2,2 mac) and M(3,2 mac), are oxidized in chloroform at room temperature under atmospheric conditions in the presence of Cu(hfa) 2 ؒ(H 2 O) 2 to the oxamide (N-CH 2 -CH 2 -N-to N-CO-CO-N-). If Cu(hfa) 2 ؒ(H 2 O) 2 is present in stoichiometric amounts the isolated product of the reaction is the dinuclear complex, M(3,2 oxomac)Cu(hfa) 2 . The dinuclear complex can also be prepared by direct reaction of M(3,2 oxomac) (prepared by another method) with Cu(hfa) 2 ؒ(H 2 O) 2 . The dinucleation reaction of M(3,2 oxomac) with M(hfa) 2 is quite general but the ligand oxidation of M(3,2 mac) is specific for Cu(hfa) 2 ؒ(H 2 O) 2 . Reaction of Cu(3,2 mac) with Hhfa or H 2 (3,2 mac) with Cu(hfa) 2 ؒ(H 2 O) 2 results not in oxidation of the macrocycle but in protonation to give Cu{H 2 (3,2 mac)}(hfa) 2 . The oxidation of Cu(3,2 mac) in an 18 O 2 atmosphere does not result in a significant incorporation of 18 O. However, nearly quantitative incorporation of 18 O is achieved when the reaction is carried out under air in the presence of H 2 18 O. The structures of Cu(3,2 mac), Cu(3,2 oxomac), Cu(3,2 oxomac) Cu(hfa) 2 and Cu{H 2 (3,2 mac)}(hfa) 2 are reported.