Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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diethylamine : NH(CH2CH3)2
copper sulfate penta hydrate : CuSO4 . 5H2O
nickel sulfate : NiSO4 . 6H2O
Class:
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elem=N,Ni,Cu
coordination
Summary:
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Diethylamine does not as easily form typical ammine-like complexes, like
ammonia.
Description:
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Add an excess amount of a solution of diethylamine to a solution of nickel
sulffate: A pale green precipitate is formed.
Add some 15% ammonia to the solution with the green precipitate: The
precipitate dissolves and the liquid turns blue.
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Add an excess amount of a solution of diethylamine to a solution of copper
sulfate: A bright blue precipitate is formed.
Add some 15% ammonia to the solution with the blue precipitate: The precipitate
dissolves and a deep royal blue clear solution is obtained.
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The diethylamine causes precipitation of the metal ions, due to formation of
hydroxide:
(CH3CH2)2NH + H2O <---> (CH3CH2)2NH2(+) + OH(-)
M(2+) + 2 OH(-) ---> M(OH)2
Here M is Ni or Cu.
No complex formation occurs.
When ammonia is added, then the ammonia coordinates to the metal ion and
releases the hydroxide ions again. This causes the precipitate to redissolve
again.
Apparently, the diethylamine does not coordinate well to metal ions, although
this is analogous to ammonia (it has a free electron pair on the nitrogen
atom).