Komplexe mit makrocyclischen Liganden I. Mechanismus der Komplexbildung zwischen Ni2+ und 1,4,8,11‐Tetraazacyclotetradecan

The kinetics of the formation of the NiII‐complex with 1,4,8,11‐tetraazacyclotetradecan (Cyclam) are studied by spectrophotometric and potentiostatic methods. The reaction of Ni2+ with the cyclic ligand is about 30000 times slower than with the open chain triethylenetetraamine (Trien). Therefore the rate determining step with Cyclam can not be the dissociation of the first coordinated water molecule, as it is usually in complexation reactions, but it must be the formation of the second coordinative bond. This is considered to be due to the more rigid structure of Cyclam in comparison with Trien.