Ammonium hexachloroplatinate
Ammonium hexachloroplatinate, also known as ammonium chloroplatinate, is the inorganic compound with the formula (NH4)2[PtCl6]. 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 NH4Cl, its solubility is only 0.0028 g/100 mL.
Preparation and structure
The compound consists of separate tetrahedral ammonium cations and octahedral [PtCl6]2− anions. It is usually generated as a fine yellow precipitate by treating a solution of hexachloroplatinic acid with a solution of an ammonium salt.[1] The complex is so poorly soluble that this step is employed in the isolation of platinum from ores and recycled residues.[2]
As analyzed by X-ray crystallography, the salt crystallizes in a cubic motif reminiscent of the fluorite structure. The [PtCl6]2− centers are octahedral. The NH4+ centers are hydrogen bonded to the chloride ligands.[3]
Uses and reactions
Ammonium hexachloroplatinate is used in platinum plating. Heating (NH4)2[PtCl6] under a stream of hydrogen at 200 °C produces platinum sponge. Treating this with chlorine gives H2[PtCl6].[1]
Ammonium hexachloroplatinate decomposes to yield platinum sponge when heated to high temperatures:[1][4]
- 3(NH4)2PtCl6 → 3Pt(s) + 2NH4Cl(g) + 16HCl(g) + 2N2(g)
Safety
Dust containing ammonium hexachloroplatinate can be highly allergenic. "Symptoms range from irritation of skin and mucous membranes to life-threatening attacks of asthma."[5]
Related compounds
References
Template:Ammonium salts Template:Platinum compounds
- ↑ a b c Script error: No such module "citation/CS1".
- ↑ Cotton, S. A. Chemistry of Precious Metals, Chapman and Hall (London): 1997. Template:ISBN.
- ↑ Verde-Gómez, Y.; Alonso-Nuñez, G.; Cervantes, F.; Keer, A. "Aqueous solution reaction to synthesize ammonium hexachloroplatinate and its crystallographic and thermogravimetric characterization" Materials Letters, 2003, volume 57, p 4667-4672. Script error: No such module "doi".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".