The Mechanism of Base Hydrolysis for Co-III(NH3)(5)X2+ Ions. Hydrolysis and Rearrangement for the Sulfur-Bonded Co(NH3)(5)SCN2+ Ion

The base hydrolysis of a set of (NH3)(5)COX2+ ions (X = Cl, Br, I, NO2) in the presence of anions such as N-3(-) and NCS- shows that the rate of entry of the extraneous anion is coincident with the rate of loss of X. The preparation of the S-bonded isomer [(NH2)(2)CoSCN)Cl-2 center dot 1.5H(2)O is also described. The base hydrolysis of this isomer follows two paths, one leading to the N-bonded isomer (24%) and the other to the hydroxo complex. The former path occurs without exchange with (NCS-)-C-14 in solution. The latter path shows the same competition characteristics as observed for the chloro, bromo, iodo, and nitrato complexes. The results in this study complement those in support of the S(N)1CB mechanism for base hydrolysis in pentaamminecobalt(III) complexes. Some results for the rearrangement of CoSCN -> CoNCS in dilute acid and in the solid state are also given.