Bis ethylenediamine copper II Diiodocuprate I

Submitted by George W. Polly, Darryl E. Jackson, and Burl E. Bryant  

Although the hydrated copper(II) ion is readily reduced (o insoluble copper(I) iodide by iodide ion, the bis(ethyl-enediamine)copper(II) ion is not so reduced. Similarly, although water-soluble simple copper(I) salts cannot be isolated because of ready oxidation to copper (II) species, complex copper(I) species, suchas the iodocuprate(I) ions,1-3 [Cul2] and [Cul3],= are resistant to oxidation. The compound bis(ethylenediamine)copper(II) diiodocuprate(I) is thus an interesting example of stabilization of both oxidation states of copper through coordination.4 

Bis(ethylenediamine)copper(II) iodide has been prepared by passing air through a mixture of ethylenediamine and copper(I) iodide heated at 60°.5 Iodocuprate(I) compounds have been obtained by dissolving copper(I) iodide in concentrated alkali metal or ammonium iodide solutions. Bis(ethylenediamine)copper(II) diiodocuprate-(I) could be obtained by combining its components, but an adaptation of the procedure of Harris,3 as given here, obviates isolation of the bis(ethylenediamine)copper(II) ion and is somewhat more rapid. 

Ten grams of practical (70 to 75%) ethylenediamine is added with stirring to a solution of 12.5 g. of copper(II) sulfate 5-hydrate (0.05 mol) in 50 ml. of water. To this solution, 21.4 g. of barium iodide 2-hydrate (0.05 mol) dissolved in 50 ml. of water is added slowly with stirring. The precipitated barium sulfate is removed by filtration and is washed twice with 25-ml. portions of distilled water. The washings and the filtrate are combined. 

In a boiling solution of 120 g. of potassium iodide (0.72 mol) in 150 ml. of water, 19.05 g. of copper(I) iodide (0.10 mol) is dissolved. The solution is filtered while hot, reheated to boiling, and then added with stirring to the boiling solution of bis(ethylenediamine)copper(II) iodide. Precipitation begins immediately. The suspension is allowed to cool to room temperature and the brown crystalline product removed by filtration. The crystals are washed with five 100-ml. portions of cold water and 

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Bis (ethylenediamine)copper (II) diiodocuprate(I), 5 16, 17 Bis (ethylenediam ine) copper (II) iodide, formation of, from bis-(ethy lenediamine) copper (II) diiodocuprate(I), 5 18 Bis(ethylenediamine)nickel(II) chloride, 6 198 Bismuth(III) iodide, 4 114 Bismuth magnesium nitrate, 2Bi-(N0,)3-3Mg(N0,), 24H,0, separation of europium from samarium and gadolinium by, 2 57... 

Bis(ethylenediamine)copper(II) diiodocuprate(I) is a chocolate-brown, crystalline compound which melts with decomposition at 267°. It is insoluble in cold water and in organic solvents such as ethanol, acetone, and ethyl ether. Boiling water decomposes it immediately to insoluble copper(I) iodide and a purplish-blue solution of bis-(ethylenediamine) copper(II) iodide. The solid instantaneously reduces a cold aqueous silver nitrate solution to elemental silver. 

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