UPTAKE OF OXYGEN BY AMMONIACAL COBALT(2) SOLUTIONS

The rapid and reversible uptake of O2 by ammoniacal cobalt(II) solutions has been examined. Equilibrium constants for the oxygenation process have been determined in aqueous ammonia solution containing 2 M NH4NO3. The pentaammine reacts rapidly with O2, and second-order rate constants and associated activation parameters have been measured for this process. In high ammonia concentrations there is evidence for lower reactivity of the hexaammine, but this is not unambiguous. The tetraammine and lower species do not pick up O2 over relatively long periods of time. The decomposition (using EDTA in ammonia solution) of the oxygenated species generated in situ yields identical rates and activation parameters to those exhibited by the well-characterized solid [(NH3)5CoO2Co(NH3)5](NO3)4, dissolved in concentrated aqueous ammonia. © 1969, American Chemical Society. All rights reserved.