Metal chelates of sulphur-containing polyamine macrocycles and oxygenation of the corresponding cobalt(II) complexes

Abstract

The protonation and complex formation of macrocyclic polyamines containing a sulphur donor atom, 1-thia-4,7,10-triazacyclododecane (L⁴) and 1-thia-4,7,11,14-tetra-azacyclohexadecane (L⁵), have been investigated with the metal ions Co^II, Ni^II, Cu^II, Hg^II, and Fe^II. The equilibrium and kinetic constants for formation of the dioxygen adducts of the cobalt(II) chelates in aqueous solutions are also reported, and compared with previous data for the analogous macrocycles containing nitrogen, oxygen, and pyridine instead of sulphur. The values of log K_ML for the macrocyclic polyamines follow the trend N > S > O. Oxygenation of the cobalt(II) complexes of L⁴ and L⁵ yields µ-peroxo-adducts as with the nitrogen and oxygen analogues, and the O₂-affinity order is N S > O.