Emission Mössbauer Study Of "Cobalt Peroxide"
Emission Mössbauer Study Of "Cobalt Peroxide". Pankratov D.A., Portachenko T.A., Perfil'ev Yu.D. //Moscow University Chemistry Bulletin. 2008. V.49. №5. P.292-296.
The product interaction cooled alcohol solutions of the cobalt (II) chloride with hydrogen peroxide as described as CoO2 studied by emission Möessbauer spectroscopy. We show that dark green product is the cobalt (III) oxide.
A considerable number of cobalt complexes are known in which cobalt is bound by the coordination bond to the dioxygen group. These compounds are mixed-ligand complexes with the coordination sphere containing, in addition to the dioxygen group, other ligands completing the coordination polyhedron of the central atom to an octahedron. Depending on the number of complex-forming atoms involved in bonding to the dioxygen ligand, mononuclear complexes and binuclear complexes (in which the O–O group act as a bridge) are distinguished. In both cases, depending on the redistribution of electron density between the transition metal and dioxygen group, compounds are described as peroxo or superoxo compounds of cobalt (III) (for mononuclear complexes) and (III, III) or (III, IV) (for binuclear complexes).
The only dioxygen compound of cobalt (II) with a “simple” composition is so-called cobalt peroxide obtained by treating a cooled water–alcohol solution of cobalt chloride and hydrogen peroxides with a sodium hydroxide solution. This procedure was repeatedly reprinted in the classical handbook on preparatory techniques. Based on the thermal decomposition data, the dark green crystalline compound was identified as cobalt peroxide CoO2. Such a compound is rather extraordinary taking into account the high mobility and donor properties of electrons in the antibonding orbitals of the peroxide ion, which should increase the electron density at the cobalt(II) atom. At the same time, this compound can be formally considered as cobalt (IV) oxide, which does not contradict the formula reported in.
The charge state of the cobalt atom can be unambiguously judged from emission Mössbauer spectroscopy data, which demonstrated that, in iron–oxygen compounds, there is a correlation between the isomer shift and the oxidation state of iron atoms that form upon the decay of cobalt atoms and retain their oxidation state. Therefore, this study deals with the determination of the charge state of cobalt in this compound by emission Mössbauer spectroscopy.
Thus, emission Mössbauer spectroscopy showed that the substance obtained by the procedure in cannot be cobalt (II) peroxide; rather, it is a cobalt (III) compound (evidently, hydrated oxide).