Raman and Infrared Spectra of μ-O2 Dicobalt(III) Complexes

Raman and infrared spectra of μ-hyperoxo and μ-peroxo ammine and cyano dicobalt(III) complexes have been studied and isotopic shifts of ν(OO) and ν(CoO) examined using 18O. A μ-hyperoxo complex, [(NH3)5Co(O2)Co(NH3)5]X5 shows peaks around 1110, 620, and 440 cm−1 assignable to ν(OO), sν(CoO), and asν(CoO), respectively, whereas a μ-peroxo complex, [(NH3)5Co(O2)Co(NH3)5]X4 shows peaks around 805, 645, and 545 cm−1 assignable to ν(OO), sν(CoO), asν(CoO), respectively. These observed values are best reproduced, when the following force constants are assumed in the UBFF calculation: K(OO)=5.6, K(CoO)=1.40 mdyn/Å for μ-hyperoxo complexes and K(OO)=2.7, K(CoO)=2.15 mdyn/Å for μ-peroxo complexes. The calculated isotopic shifts are in good agreement with the observed ones. Raman and infrared spectra of dibridged μ-amido-μ-O2 (both peroxo and hyperoxo) dicobalt(III) complex have also been characterized. A linear relationship has been found between ν(OO) and the bond order of the O2 moiety in O2-complexes in different oxidation states including alkali hyperoxide, alkali peroxide, hydrogen peroxide, oxygen, and O2+ species.