energetic tetraamminecopper(ii) salts

The complex ion of ammonia and Copper(II) forms a number of energetic salts with strongly oxidizing anions. 

Tetraamminecopper(ii) sulphate

TACS, [Cu(NH3)4(H2O)n]SO4

To a 250ml beaker, I added copper(ii) sulphate pentahydrate (25g, 0.1001 moles), water (25ml) and 25% ammonia solution (40ml, 9.03g NH3, 0.5302 moles NH3). With stirring, almost all the copper(ii) sulphate dissolved giving a rich dark blue coloured solution. I filtered the solution to remove any undissolved copper(ii) hydroxide and copper(ii) sulphate. To a the filtrate, I then added ethanol (38ml), whereupon a large amount of dark blue-purple precipitate formed. This should be the product, tetraamminecopper(ii) sulphate. I filtered off the precipitate, using the filtrate to wash the remaining solids in the beaker onto the filter. Finally I washed the product on the filter with 25% ammonia solution (5ml), ethanol (15ml), then acetone (15ml) and allowed the product to dry.

Yield: 18.64g (76% assuming monohydrate) of tetraamminecopper(ii) sulphate as a dark purple-blue crystalline powder

Tetraamminecopper(ii) bis(permanganate)

TACPM, [Cu(NH3)4(H2O)n](MnO4)2

In a 200ml conical flask, I dissolved tetraamminecopper(ii) sulphate (5g, 0.0203 moles) in water (30ml), giving a rich dark blue solution. I then chilled the solution down to 8 C and added cold saturated potassium permanganate solution (31ml). Without delay, I chilled the mixture down to 2 C, then filtered off the precipitated product immediately, pressing it on the filter to remove as much liquid as possible. The product was then allowed to dry.

Yield: 1.2g (15% assuming monohydrate) of tetraamminecopper(ii) bis(permanganate) as a brown, slightly violet powder

TACPM powder

Tetraamminecopper(ii) persulphate

TACPS, [Cu(NH3)4(H2O)n]S2O8

To a 200ml conical, I added tetraamminecopper(ii) sulphate (5g, 0.0203 moles) and water (25ml). With swirling, the tetraamminecopper(ii) sulphate dissolved, giving a beautiful dark blue solution. Using a graduated cylinder, I then poured in a solution of ammonium persulphate (5.13g, 0.0225 moles, 10% excess) in water (20ml). The flask was swirled, then chilled in a refrigerator for 1 hour, whereupon a mass of dark blue crystals separated. This should be the tetraamminecopper(ii) persulphate. The product was filtered off, pressed on the filter, then allowed to dry.

Yield: 3.37g (48% assuming monohydrate) of tetraamminecopper(ii) persulphate as fine deep purple-blue crystals

TACPS crystals

Tetraamminecopper(ii) dinitrate

TACN, [Cu(NH3)4(H2O)n](NO3)2

To a 500ml, two-neck round-bottom flask, I added copper metal turnings (5g). In the centre neck I placed a double jointed 250ml separatory funnel filled with 19ml of 68% nitric acid (stopcock closed). The 19ml of 68% nitric acid was prepared by by carefully diluting 13ml of anhydrous nitric acid with 6ml of water. To the other neck of the flask, I attached a vacuum adaptor with its other end sealed with a stopper. I then attached one end of a long PVC tube to the vacuum port on the adaptor with the other end of the tube leading to a bubbler trap containing sodium hydroxide solution. The trap serves to neutralize the highly toxic nitrogen dioxide gas produced in the reaction. Anyway, Once everything was ready, I slowly opened the stopcock on the addition funnel and allowed the nitric acid into the round-bottom flask containing the copper. lots of bubbling occured and large amounts of red nitrogen dioxide gas where given off. Once the reaction seemed to be largely complete, I added water (60ml) thourgh the separatory funnel. The green contents off the flask became more blue and most of the remaining nitrogen dioxide in the flask was driven off or dissolved. A small amount of bubbling copper remained so I disconnected the flask and allowed it to stand for a few days to insure the reaction was complete. I then poured the deep blue copper(ii) nitrate solution into a 150ml beaker and allowed approximately 2 thirds of the liquid to evaporate off.

To the concentrated solution, I then added 32ml of 25% ammonia solution. I large amount of heat was given off and a precipitate formed. I stirred the mixture, pressing the precipitate against the sides of the beaker, whereupon it appeared to redissolve. Upon cooling, a large amount of dark blue crystals precipitated. This should be the tetraamminecopper(ii) dinitrate. Once the mixture had cooled completely to room temperature, I filtered off the product, pressing it well on the filter then scrapped it off into a 150ml beaker containing 20ml of acetone. The mixture was stirred well for a few minutes, then the product was filtered off and pressed again. Lastly the product was dried.

Yield: 15.9g (74% assuming monohydrate) tetraamminecopper(ii) dinitrate as dark purple-blue crystals 

TACN crystals