An unusual coordination complex of copper, producing dark blue crystals.
- Color: dark blue, almost black
- Crystal shape: tabular, flat
- Stability on air: stable
Preparation is essentially the same as of the potassium analog, with potassium replaced by ammonium. However, there is a complication: a solution containing stoichiometric mixture of [NH4]+, Cu2+, Cl-, NH2SO3- ions does not produce the desired compound upon crystallization. Instead, light blue crystals of ammonium tetrachlorocuprate appear. This can be solved by adding excess of copper sulfamate.
All copper compounds are moderately toxic.