Substitution reactions of some bis(2,2'-bipyridine) and mixed 2,2'-bipyridine, 2,2',2'-terpyridine complexes of ruthenium(II). II. The kinetics of substitution of nitrite and other nucleophiles

The rates of substitution of the complex ions [Ru11(H2O)bipytrpy]2+ and [Ru11(H2O)2 bipy2]2+, where bipy = 2,2'-bipyridine and trpy = 2,2',2"-terpyridine, by a number of nucleophilic reagents in aqueous solution, have been determined as a function of temperature. The reactions were observed to be second order and rates fall in the sequence Ni > NO2 > SCN-> pyridine. The range of Arrhenius parameters is very large with some unusually low frequency factors. The diaquo complex appears to undergo substitution leading to disubstituted derivatives in a single step. In the case of substitution by nitrite, there is evidence that the final products are nitro complexes formed by rapid isomerization of intermediate nitrito complexes.