Copper glycine stability constants

The most persistent and stable amino acids appear to be glycine, aspartic acid, and glutamic acid, which were reported in Paleozoic anthracite from Great Britain by Heijhenskjold and Mollerberg (8). Among the most stable amino acid chelates are those formed with copper however, the stability constants for the a-amino acids of copper do not differ to the point where they indicate that the above mentioned three acids would be preferentially preserved. 

Because /3 is the symbol for the product of individual stability constants, we write j8 = KxK for the combination of copper with glycine and for all other cases where a metal becomes saturated after combining with two portions of a ligand. For zinc and ethylenediamine, where the zinc becomes saturated after fixing three portions of the ligand, we write = KxK2K and, for the complex of a metal that is saturated when it has combined with one unit of ligand (for instance, zinc and EDTA), = Kx. 

Solvolysis of Organic Ligands.— The catalysis of hydrolysis of organic esters by metal ions or complexes has been much studied for many years. Recent examples of kinetic studies include hydrolysis of oxalate esters catalysed by a variety of ions, and of the bis[-L-(-J-)-histidine methyl ester] complexes of copper(n) and of nickel(n). The relative catalytic effects of several copper(n) complexes, including Cu(imda), Cu(nta), and Cu(dien) +, on the hydrolysis of methyl glycinate have been determined. Rate constants for base hydrolysis of this ester correlate with stability constants for mixed complexes of this ester with the above-named copper(n) complexes. ... 

The glycine complex of cobalt(n)-bipy, like that of copper(n>-bipy, has a comparatively high stability constant relative to the bis-glydnate of the metal. It has been shown that this can be attributed to a lower dissociation rate constant for the former (55 s at 25 °C) than for the latter (330 s ), the formation rate constants being rather similar (1.6 x 10 and 2.0 x 10 1 mol s respectively). 

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