Solvent effects on the kinetics of the reactions of nickel(II) and cobalt(II) ions with 2,2′-bipyridyl and 2,2′,2″-terpyridyl

The rates and activation parameters for substitution of bipyridyl and terpyridyl at NiII and CoII ions have been measured in water and some non-aqueous solvents. A comparison is made with the corresponding rates of solvent exchange for these ions, and the applicability of the model usually suggested for aqueous solutions is examined. The behaviour of water is apparently not general. Approximate relationships are described linking the divergence of substitution rates from exchange rates with properties of the solvent which reflect its structure, such as its enthalpy of evaporation and its fluidity.