The formation of monomeric dioxygen adducts of cobalt(II) complexes with ammonia, methylamine and ethylenediamine in an Amberlyst A-15 cation exchange resin is demonstrated by EPR. The EPR spectra are compared with those of the corresponding adducts formed in zeolite Y. The enhanced stability of the monomeric adducts in Amerlyst is attributed to the interaction of the complexes with sulfonate anion sites in the resin. The total amounts of oxygen adsorbed are greater than the spin concentrations of the monomeric adducts and this discrepancy is attributed to the formation of diamagnetic µ-peroxodicobalt adducts as well as a slow irreversible oxidation of the Co(II) to Co(III). A paramagnetic µ-superoxodicobalt adduct is observed only with methylamine and then only in very low concentrations.