Study of the base‐catalyzed nitrito–nitro isomerization reaction ([(NH₃)₅Co‐ONO]²⁺ → [(NH₃)₅Co‐NO₂]²⁺) in mixed solvents

Abstract

The base-catalyzed linkage isomerization of [Co(NH 3 ) 5 -ONO] 2+ to the nitro [(NH 3 ) 5 Co-NO 2 ] 2+ form is studied in various isodielectric water-cosolvent mixtures (methanol, ethanol, tert-butyl alcohol, and 2-propanol) at 298 K. In all cases, except for methanol-water mixtures, the rate constants increase with the proportion of cosolvent. Medium effects have been rationalized by using a multiparameter regression of solvent parameters which rationalizes the results obtained, including water-methanol mixtures. The experimental data, k 2 , in fact, are well correlated through the following equation:where A, B, and G exc are the acidity parameter, the basicity parameter, and the excess Gibbs free energy of the mixture, respectively. C