Aminopolycarboxylate ligands

Hydroxide clusters supported by (poly)aminopolycarboxylate ligands... 

The aminopolycarboxylate ligand also increases the rate of the Cr -HaO reaction. The stoicheiometry of formation of the peroxochromium(iv) complex and its decomposition to Cr have been studied over the range [H+]=0.1— 3.0M. For the reactions... 

N.m.r. studies of ligand exchange involving aminopolycarboxylate ligands include those of egta at calcium(ii) and of edta at magnesiura(ii), calcium(ii), and strontium(ii). The relative importance of dissociative and associative (i.e. via an L—M—L intermediate) paths has been assessed, and the reactivities of variously protonated and deprotonated forms of the ligands and the complexes have been considered. 

Goedken, and Gritmon(J3) in 1977 to investigate the thermodynamic parameters of a variety of aminopolycarboxylate ligands across the lanthanide series. Variations in the enthalpy and entropy curves vs. Z were attributed to different degrees and patterns of dehydration as well as the increasing polydentate nature of the complexation. The linear relationship between log 6 and ZpKa of... 

Figure 4. Thermodynamic parameters of Sm(III) complexation with selected aminopolycarboxylate ligands. Adapted from ref. 54.

The exchange of a radioisotopic lanthanide for a stable lanthanide metal chelated to an aminopolycarboxylate ligand has been found to proceed via two mechanistic pathways(tiO). Below pH 6, an acid-catalyzed mechanism predominates in which protonation catalyzes decomposition of die lanthanide-aminopolycarboxylate complex. The uncomplexed ligand chelates with free lanthanide cations in solution. The mechanism below illustrates the acid-catalyzed pathway, where A = aminopolycarboxylate ligand (t denotes the activated complex Ln is die radioactive tracer). 

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