FORMATION AND HOMOLYSIS OF A MONONUCLEAR COBALT OXYGEN ADDUCT

The macrocyclic cobalt(II) complex (H2O)nCo(C-meso-Me6[14]aneN4)2+ (L2Co2+) binds oxygen to yield L2CoO22+. The rate constants for the binding and release of O2 in aqueous solutions at25°C have values 5.0 × 106 M-1 s-1 and 1.66 × 104 s-1, respectively. There is no evidence for the formation of a binuclear μ-peroxo complex. The ESR parameters of the oxygen adduct in toluene at 120 K, g‖ = 2.108, g⊥ = 1.96, A‖ = 3.81 × 10-3 cm-1, A⊥ = 2.94 × 10-3 cm-1, are consistent with the formulation of the complex as a 1:1 adduct with the unpaired spin density residing on the oxygen. The laser flash photolysis of L2CoO22+ (Xlrr 490 nm) induces the cleavage of the cobalt-oxygen bond, L2CoO22+ hν L2Co2+ + O2. © 1990, American Chemical Society. All rights reserved.