Ammonium hexachloroplatinate, also known as ammonium chloroplatinate, is the inorganic compound with the formula (NH<sub>4</sub>)<sub>2</sub>[PtCl<sub>6</sub>]. It is a rare example of a soluble platinum(IV) salt that is not hygroscopic. It forms intensely yellow solutions in water. In the presence of 1M NH<sub>4</sub>Cl, its solubility is only 0.0028 g/100 mL.
The compound consists of separate tetrahedral ammonium cations and octahedral [PtCl<sub>6</sub>]<sup>2−</sup> anions. It is usually generated as a fine yellow precipitate by treating a solution of hexachloroplatinic acid with a solution of an ammonium salt. The complex is so poorly soluble that this step is employed in the isolation of platinum from ores and recycled residues.
As analyzed by X-ray crystallography, the salt crystallizes in a cubic motif reminiscent of the fluorite structure. The [PtCl<sub>6</sub>]<sup>2âÂÂ</sup> centers are octahedral. The NH<sub>4</sub><sup>+</sup> centers are hydrogen bonded to the chloride ligands.
Ammonium hexachloroplatinate is used in platinum plating. Heating (NH<sub>4</sub>)<sub>2</sub>[PtCl<sub>6</sub>] under a stream of hydrogen at 200 ðC produces platinum sponge. Treating this with chlorine gives H<sub>2</sub>[PtCl<sub>6</sub>].
Ammonium hexachloroplatinate decomposes to yield platinum sponge when heated to high temperatures:
Dust containing ammonium hexachloroplatinate can be highly allergenic. "Symptoms range from irritation of skin and mucous membranes to life-threatening attacks of asthma."