Magnesium complexes ammines

Calcium, strontium and barium form some poorly characterised /9-diketone complexes and rather unstable ammines tendency to covalence, even as indicated by hydration of the ions, has decreased with cation size. The determination of magnesium and calcium with sodium ethylenediamine tetra-acetate, e.d.t.a., probably involves the formation of a chelate complex whose stability is enhanced by the presence of 5-membered rings. 

The normal product of reduction of an oxime is a primary amine but when the oxime of a benzenoid aldehyde was treated with magnesium and ammonium acetate at 50°, the nitrile was formed [64]. By reacting an aldehyde with a cobalt ammine, Co(NH3)6 [Co(CO)4] 2, and subsequent oxidation of the complex with bromine, the nitrile was formed [65]. 

When zinc and magnesium containing iron are dissolved in dilute hydrochloric acid, the solution contains not only zinc and magnesium chloride but also iron chloride. However, under these conditions, the iron does not respond to a,a -dipyridyl directly unless no more than traces of iron are involved. The sensitive test for valent iron fails because Zn+ and Mg+ ions form colorless complex ions with a,a -dip3rridyl and thus consume the reagent. However, this interference can be averted, if concentrated ammonium hydroxide is added after the a,a -dipyridyl has been introduced. The zinc and the magnesium dipyridyl compounds are converted into the respective ammine ions and the reagent is released and made available to the ferrous ions. 

We must note that this expression is legitimate only if the ammine complexes concentrations are negligible in the mass balance relation on the buffer.) Developing the stability constants expressions as a function of the concentration of magnesium... 

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