Tris diamine chromium III Salts

CrCI3-6H20 + 3 diamine [Cr(diamine)3]Cl3-3H20 + 3H20 

Tris(diamine) complexes of chromium(III) have been important from several viewpoints. First, the tris(ethylenediamine) complex is valuable as a synthetic intermediate,1 the action of heat on the chloride salt giving the cis-dichlorobis(ethylenediamine) complex and on the thiocyanate salt giving the irans-bis(iso-thiocyanato) complex. Second, the cations are resolvable, and studies2 of their optical activity have been fruitful in establishing relations between signs of Cotton effects and absolute stereochemistries. A large number of other studies, including kinetic and equilibrium measurements, have shown these complexes to be readily hydrolyzed to bis(ethylenediamine) complexes.3 

Previous synthetic routes, although chemically simple, are operationally tedious  

It has been found4 that a good yield may be obtained rapidly by allowing the commercially available green chromic chloride, CrCl8-6H20, in methanol to boil under reflux with ethylenedi-amine in the presence of metallic zinc. The product, hydrated tris(ethylenediamine)chromium(III) chloride, is obtained as a solid and is readily purified. An exactly similar procedure may be used for the complex of 1,2-propanediamine. 

The zinc catalyst probably functions by generating kinetically labile chromium(II) species. The present observation is reminiscent of several others, notably (1) the ready dissolution of anhydrous chromium(III) chloride in water and other solvents only in the presence of chromium(II) ion or reducing agents, 

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