Tris ethylenediamine chromium III Salts

The chromium (III) ammines closely resemble the corresponding cobalt(III) complexes in many respects. For example, analogous compounds in the two series are usually isomorphous and of similar color. While the preparative methods used for cobalt (III) ammines can sometimes be employed for the preparation of the corresponding chromium (III) ammines, other methods are usually preferred. Thus a mixture of a chromium (II) salt and ethylenedia-mine absorbs atmospheric oxygen even more readily than does a mixture of a cobalt (II) salt and the base. The procedure for preparing tris(ethylenediamine)chromium(III) 

Molecules that coordinate strongly can often displace others from the coordination sphere. Ethylenediamine does not readily replace water from the hydrated chro-mium(III) ion, but it does readily displace pyridine. Pfeiffer has described the preparation of tris (ethylenediamine) chromium(III) chloride from trichlorotripyridine-chromium and the corresponding sulfate from dehydrated chrome alum.  

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The method outlined here is similar to the latter but obviates the separation of potassium sulfate from the product. The new methods described below for obtaining various tris (ethylenediamine) chromium(III) salts with anhydrous chromium(III) sulfate as the starting material can be used also for preparing the corresponding propylenediamine derivatives. ... 

The tris(ethylenediamine)chromium(III) salts (luteo chromic salts) are all markedly crystalline, orange-yellow substances. While the suKate is. extremely soluble and the chloride highly soluble in water, the bromide, iodide, and thiocyanate are relatively insoluble. All of these salts are slowly decomposed in cold water and rapidly in hot water, forming deep-red gummy materials, which are evidently hydroxoamminechromium compounds. The dry salts are slowly decomposed by exposure to light. The dry chloride and thiocyanate are decomposed readily by heat to bis(ethylenediamine) salts (synthesis 61). 

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