KINETICS OF EXTREMELY FAST LIGAND-EXCHANGE REACTIONS WITH METHYLMERCURY(II)-COMPLEXES OF 1-METHYLPYRIDINE-2-THIONE AND 1-METHYL-QUINALDINE-4-THIONE - RATE-EQUILIBRIA CORRELATIONS

Methylmercury(II) transfer from two heterocyclic thiones to a wide variety of other ligands and the reverse reaction have been investigated by the temperature‐jump method. The reactions are almost diffusion controlled, even when the free energy difference is negligible. The only exceptions are reactions to and from hydroxide. They are about hundred times slower than those with other ligands of comparable stability at zero free energy difference. This is in agreement with the behaviour of hydroxide in other methylmercury(II) exchange reactions. They follow an associative reaction mechanism. An empirical correlation of rate‐and equilibrium‐constants for atom transfer reactions is proposed. This equation shows some similarities to that of the Marcus type for atom transfer. However, the proposed equation not only describes reactions governed by an associative mechanism, but also those of dissociative type and cases between the two extremes. Copyright © 1979 Verlag GmbH & Co. KGaA, Weinheim