The ligand unwrapping/rewrapping pathway that exchanges metals in -acetylated, hexacoordinate NSO complexes.

The effect of -acetylation in MNS complexes on metal exchange reactivity was examined in a series of MNSO complexes. While clean exchange processes do not occur for the MNS derivatives where formation of -bridged aggregates predominate, acetylation permits the metal exchange with hierarchy that follows the Irving-Williams series of stability for first row transition metals: Fe < Co < Ni < Cu > Zn. The rate determining step consistent with kinetic parameters depends on both M and M', supporting a mechanism of exchange that involves ligand unwrapping/rewrapping process as earlier defined by Margerum for M(EDTA) systems. The enhanced metal exchange deriving from -acetylation is of significance to probes and detection of cysteine- metallo-proteins and metallo-enzyme active sites, and highlights a new role for -acetylation.