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Author: Subject: Has anyone grown nice crystals of tetraamminecopper(II) sulfate?
SuperOxide
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[*] posted on 20-6-2021 at 08:58
Has anyone grown nice crystals of tetraamminecopper(II) sulfate?


Lately I've gotten into making nice looking crystals of colorful compounds, and I have a decent amount of copper sulfate that's just been sitting around, so I decided to use it in some reactions since it makes many different pretty blue/green/purple compounds (eg: copper aspirinate, copper acetate, etc).

The one I'm currently working on is Tetraamminecopper(II) sulfate, and while I've gotten the synth to work just fine, and the color is amazingly beautiful, I can't get decent crystals to grow. If you look at the picture on Wikipedia:

You can see how amazing they can be, if only I can grow some decently sized crystals...

The compound is soluble in water and insoluble in alcohols (I've been using MeOH), and I've tried a few different things:

  1. Adding in a very small amount of MeOH very slowly, which just results in the powder (kinda expected this).
  2. Adding absolutely no MeOH, and just letting it sit for 4 days to see if some crystals would form
  3. Doing the same thing as above, but leaving it uncovered so the water could slowly evaporate out
  4. doing a hot filtration then letting it cool slowly by keeping it insulated

The only one that I thought looked like it may have started to grow crystals was #2 in the above list, but when I just barely moved the erlenmeyer flask to get a photo of it, all the solids just fell to the bottom as a powder (so obviously not crystals).

If anyone has managed to grow nice crystals of these, let me know what technique you used.

Thanks.




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[*] posted on 20-6-2021 at 09:55


That’s one of woelen’s pictures… so clearly he knows how to do it



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[*] posted on 20-6-2021 at 11:18


Quote: Originally posted by Texium  
That’s one of woelen’s pictures… so clearly he knows how to do it
Oh wow, I didn't know that. Just got it from Wikipedia.

Hopefully he'll chime in.




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[*] posted on 20-6-2021 at 11:28


Well, I made the explosive tetraamine copper nitrate, and this was the procedure I followed:
1) React CuSO4 root remover with NaOH to give Cu(OH)2
2) Filter off the precipitate
3) React with nitric acid to give Cu(NO3)2 solution
4) Add NH4OH solution till pH is strongly basic
5) Add in 50% of the solution's volume in iPOH
6) Put into a Styrofoam Chinese food container filled with ice water and leave it there for half an hour
7) Filter off the crystals

You can skip the Cu(NO3)2 solution prep if you already have copper sulfate root remover. Or, you can dissolve copper in nitric acid, add NaOH, and then add H2SO4 if you don't have copper sulfate on hand.




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[*] posted on 20-6-2021 at 11:48


Quote: Originally posted by Triflic Acid  
Well, I made the explosive tetraamine copper nitrate, and this was the procedure I followed:
1) React CuSO4 root remover with NaOH to give Cu(OH)2
2) Filter off the precipitate
3) React with nitric acid to give Cu(NO3)2 solution
4) Add NH4OH solution till pH is strongly basic
5) Add in 50% of the solution's volume in iPOH
6) Put into a Styrofoam Chinese food container filled with ice water and leave it there for half an hour
7) Filter off the crystals

You can skip the Cu(NO3)2 solution prep if you already have copper sulfate root remover. Or, you can dissolve copper in nitric acid, add NaOH, and then add H2SO4 if you don't have copper sulfate on hand.


I did get a few bottles of copper sulfate root remover, and I recrystallized every bit of it and getting some nice big crystals, so I'm sure it's fairly pure.
Also, I made some Cu(OH)2 just yesterday using the copper sulfate and reagent grade 30% ammonium hydroxide (which is like 4 years old, but I don't think that matters).

Do you by any chance have pictures of your end results?




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[*] posted on 21-6-2021 at 01:52


Making these crystals can be done as follows:
- Add 10 grams of solid copper(II) sulfate 5-hydrate to appr. 35 ml of water and gently heat the liquid, until all of the solid has dissolved. Stirring helps dissolving the solid. Do not heat too much, the liquid should not be hot after dissolving the copper sulfate, just warm to the feeling of the hand.
- Add 25 ml of highly concentrated ammonia (I used 25% solution, but the higher the concentration, the better). First you get a pale blue precipitate, but on adding more ammonia, this redissolves again.
- Now carefully heat more strongly, and let the liquid boil slowly for a while. This drives off a lot of ammonia (outside! fume hood!). Boil down to 50 ml or so.
- Let the liquid cool down somewhat and then add 50 ml of luke warm ethanol (I used plain 96%, denatured, colorless ethanol).
- Let the liquid cool down to room temperature.
- Slowly let the liquid cool down further in a freezer. The colder the better (a good freezer can go to -18 C or so). But cooling down must be slow for good crystals.
- While the copper sulfate cools down, in a separate beaker, mix 40 ml of ethanol with 10 ml of concentrated ammonia and let this cool down as well in the freezer.
- Once you have a lot of nice crystals, decant the liquid from the crystals and quickly rinse a few times with the ice cold ammonia/ethanol mix and decant the supernatant liquid.
- Finally, I rinsed with 10 ml of pure diethyl ether to get most ethanol/ammonia removed as well. If you don't have diethyl ether, then rinse with 10 ml of ice cold ethanol. Decant as much as possible of the liquid and transfer to a capped bottle.
- Allow the ice cold solid (with the ethanol) to go back to room temperature in the capped bottle. This step is important, otherwise the cold solid will attract water from the air due to condensation.
- Once the bottle is not cold anymore, take out the crystals, put them on a glass fritte and on the other side put some absorbing tissue on the glass fritte. Do not put the crystals directly on paper tissue! Copper(II) tetrammine complex destroys paper, so the wet crystals should not be in contact with paper.
- Let the almost dry crystals get dry in contact with air. Try to keep this period as brief as possible, in order to avoid loss of ammonia and getting a fine pale blue powder on your crystals. For that reason, I used another rinse with diethyl ether, because that evaporates very quickly and makes it possible to dry the crystals in just a few minutes.




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[*] posted on 21-6-2021 at 15:49


Quote: Originally posted by woelen  
Making these crystals can be done as follows:
- Add 10 grams of solid copper(II) sulfate 5-hydrate to appr. 35 ml of water and gently heat the liquid, until all of the solid has dissolved. Stirring helps dissolving the solid. Do not heat too much, the liquid should not be hot after dissolving the copper sulfate, just warm to the feeling of the hand.
- Add 25 ml of highly concentrated ammonia (I used 25% solution, but the higher the concentration, the better). First you get a pale blue precipitate, but on adding more ammonia, this redissolves again.
- Now carefully heat more strongly, and let the liquid boil slowly for a while. This drives off a lot of ammonia (outside! fume hood!). Boil down to 50 ml or so.
- Let the liquid cool down somewhat and then add 50 ml of luke warm ethanol (I used plain 96%, denatured, colorless ethanol).
- Let the liquid cool down to room temperature.
- Slowly let the liquid cool down further in a freezer. The colder the better (a good freezer can go to -18 C or so). But cooling down must be slow for good crystals.
- While the copper sulfate cools down, in a separate beaker, mix 40 ml of ethanol with 10 ml of concentrated ammonia and let this cool down as well in the freezer.
- Once you have a lot of nice crystals, decant the liquid from the crystals and quickly rinse a few times with the ice cold ammonia/ethanol mix and decant the supernatant liquid.
- Finally, I rinsed with 10 ml of pure diethyl ether to get most ethanol/ammonia removed as well. If you don't have diethyl ether, then rinse with 10 ml of ice cold ethanol. Decant as much as possible of the liquid and transfer to a capped bottle.
- Allow the ice cold solid (with the ethanol) to go back to room temperature in the capped bottle. This step is important, otherwise the cold solid will attract water from the air due to condensation.
- Once the bottle is not cold anymore, take out the crystals, put them on a glass fritte and on the other side put some absorbing tissue on the glass fritte. Do not put the crystals directly on paper tissue! Copper(II) tetrammine complex destroys paper, so the wet crystals should not be in contact with paper.
- Let the almost dry crystals get dry in contact with air. Try to keep this period as brief as possible, in order to avoid loss of ammonia and getting a fine pale blue powder on your crystals. For that reason, I used another rinse with diethyl ether, because that evaporates very quickly and makes it possible to dry the crystals in just a few minutes.


Awesome! I'll give this a shot.

Luckily I have everything you detailed (concentrated ammonia, diethyl ether, ethanol, etc).
There were multiple steps in there that I didn't do, such as gently boiling it down, and the ratios of ethanol/ammonia was different for the wash as well.

I will try all of this when I get a chance and report back the results.

Thanks for chiming in woelen.




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[*] posted on 21-6-2021 at 23:05


The ratios for ethanol/ammonia are not that critical. The most critical thing is that you let cool down slowly. A slower cool down leads to bigger crystals. Another important thing is that contact with air should be as brief as possible. The complex slowly loses ammonia when in plain air and this leads to loss of the deep blue color and formation of a pale blue powdery layer on the crystals. Use of diethylether for final rinsing allows quick drying. Best is to use diethyl ether at room temperature, which is added to the crystals in the final step, also at room temperature.

Having the ice cold crystals in contact with air also is not a good thing. Cold things become wet, due to condensation of water vapor from the air. You do not want that on your crystals.




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[*] posted on 22-6-2021 at 05:17


Quote: Originally posted by woelen  
The ratios for ethanol/ammonia are not that critical. The most critical thing is that you let cool down slowly. A slower cool down leads to bigger crystals. Another important thing is that contact with air should be as brief as possible. The complex slowly loses ammonia when in plain air and this leads to loss of the deep blue color and formation of a pale blue powdery layer on the crystals. Use of diethylether for final rinsing allows quick drying. Best is to use diethyl ether at room temperature, which is added to the crystals in the final step, also at room temperature.

Having the ice cold crystals in contact with air also is not a good thing. Cold things become wet, due to condensation of water vapor from the air. You do not want that on your crystals.

Yeah, I think that may explain why some of mine went a different color:

Both of those were from the same synthesis, but I tried to crystalize one of them slower, but then let it air dry when I filtered it off (which it was very cold). And it looks like rubbish.




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