Ammonium hexachloroplatinate, also known as ammonium chloroplatinate, is the

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula (NH₄)₂ tCl₆ It is a rare example of a soluble

platinum Platinum is a chemical element; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...

(IV)

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

that is not

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...

. 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 In geometry, a tetrahedron (: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular Face (geometry), faces, six straight Edge (geometry), edges, and four vertex (geometry), vertices. The tet ...

ammonium Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) polyatomic ion, molecular ion with the chemical formula or . It is formed by the protonation, addition of a proton (a hydrogen nucleu ...

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

s and

octahedral In geometry, an octahedron (: octahedra or octahedrons) is any polyhedron with eight faces. One special case is the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex. Many types of i ...

tCl₆sup>2−

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

s. 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 X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

, the salt crystallizes in a cubic motif reminiscent of the

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scal ...

structure. The tCl₆sup>2− centers are octahedral. The NH₄⁺ centers are

hydrogen bond In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...

ed to the

chloride The term chloride refers to a compound or molecule that contains either a chlorine anion (), which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond (). The pr ...

ligands In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ...

Uses and reactions

Ammonium hexachloroplatinate is used in platinum plating. Heating (NH₄)₂ tCl₆under a stream of

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

at 200 °C produces

sponge. Treating this with chlorine gives H₂ tCl₆ Ammonium hexachloroplatinate decomposes to yield platinum sponge when heated to high temperatures: :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."

Related compounds

Potassium hexachloroplatinate Potassium hexachloroplatinate is the inorganic compound with the formula K2PtCl6. It is a yellow solid that is a comparatively insoluble potassium salt. The salt features the hexachloroplatinate(IV) dianion, which has octahedral coordination geome ...

References

{{Platinum compounds Platinum(IV) compounds Chloro complexes Ammonium compounds Hexachloroplatinates