Copper -ammine systems

The copper(II)-ammine system was the first labile metal-ligand system that had been studi in this detail and deprived of its secret of being stepwise in character. This was known to be the case also for the inert chromium(III)-thiocyanato system... 

By using a copper amalgam electrode, which in effect is a copper(I)- and copper(II)-aqua ion electrode, and a pure mercury electrode, which is a redox electrode, IB remeasured and confirmed the gross complexity constant Pa and the fifth consecutive constant for the copper(II)-ammine system and provided, in addition to a number of standard redox potentials, the two step constants of the copper(I)... 

Most systems that have been studied possess a spreading that is wider than the statistical one or, in other words, show a positive residual effect. It is therefore noteworthy that the silver(I)-ammine system (4), which, in regard to coordination numbers (77) and characterizing d configuration, is analogous to the copper(I) system, has a negative residual ect. This unexpectedly low occurrence of the silver(I)-monoammine complex - only 20% at the maximum — is not understood. However, in view of the very small standard free energy differences that we are concerned with, it will probably be a while before we come to understand the subtle difference between copper(I) and silver(I). 

Figure la contains three graphs that all represent n. The least steep graph is the "experimental" formation function that is calculated by using equation 14 together with the step constants of Table I, valid for the copper(II)-ammine system. This graph has two inflection points and > 4 for high values of log([NH3]/M)- It includes the information, ATj, about the weakly bound pentaamminecopper(II) complex. 

The graph of intermediate slope illustrates the formation of the system that has the 04 value of the copper(II)-ammine system but a statistical distribution of all complex species, TV being assumed equal to four. 

It is believed that copper acts as the oxidant in these systems, effecting the dissolution of gold as an ammine complex,... 

The most important publications dealing with multicomponent systems were those of Jannik BJerrum on copper(II)-ammine complexes (15-17) and of Holler on iron(III)- thiocyanato complexes (18). 

---