Exchange of Radiocobalt between the Hexammines of Cobalt(II) and Cobalt(III) in Liquid Ammonia

Exchange of radiocobalt between Co(NH3)6+2 and Co(NH3)6+3 nitrates in liquid ammonia has been studied at 25° and 45°C. Reactants were separated by distilling off the solvent ammonia and extracting the Co(II) as the thiocyanate complex into a mixture of ether and isoamyl alcohol. Runs were not accurately reproducible, probably because of catalytic effects from traces of oxygen in the system. Rate constants, calculated for an assumed bimolecular rate law, are 6×10—5 and 7×10—4 l·mole—1·sec—1 at 25° and 45°C, respectively. The rate in liquid ammonia is compared with published rates in aqueous ammonia solution and with the rate of exchange of labeled NH3 between solvent liquid ammonia and ligand ammonia in Co(NH3)6+3.