Cobalt EDDA -

One geometrical isomer of the cobalt (iii) complex of ethylenediamine-iViV -diacetate-iViV -dipropionate (edda) has been prepared by oxidation of C0CI2 with H2O2 in the presence of edda. It has been resolved into optical isomers and spectral evidence suggests that its structure is (107). The structure of K[ds-Co(ida)2],2.5H20 (ida = iminodiacetate) has been determined. Cobalt(iii) complexes of (S)-azetH (108) have been prepared. One isomer of... 

Recent kinetic studies of metal ion exchanges include those of europium(iii) with its cydta complex and of various lanthanides(iii) with their respective dtpa complexes. Kinetic studies of metal ion replacement include reactions of nta, edda, heedta, egta, cydta, and dtpa complexes of zinc(ii) with copper(ii), of edta nedta, cydta, and dtpa complexes of lead(ii) with cobalt(ii), of the edta complex of nickel(ii) with indium(iii), and of ttha complexes of cadmium(ii) with lanthanides(in). There are again several systems mainly concerned with 3 + and 4+ ions, for example those involving edta and dtpa complexes of lanthanides. In systems containing ions of high charge, it seems to be easier to demonstrate the existence of dinuclear intermediates of the type invoked in associative (cf. above) pathways. 

There have been a few reports over the years on nitrate catalysis of substitution at cobalt(III) and at chromium(III). Now it has been shown that nitrate has a catalytic effect on oxalate anation of a-c/5-[Co(edda)(OH2)2] - The outer-sphere association constant appears to be larger when nitrate is present. The possibility of the formation of a transient five-coordinate intermediate under the influence of the nitrate (cf. the end of the previous section, 5.7.3.) should not be ruled out. ... 

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