Ammonium hexachloroplatinate, also known as ammonium chloroplatinate, is the
inorganic compound
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemi ...
with the formula (NH
4)
2 tCl6 It is a rare example of a soluble
platinum
Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver".
Pla ...
(IV)
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quanti ...
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 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 conve ...
s and
octahedral tCl6sup>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.
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 determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angle ...
, the salt crystallizes in a cubic motif reminiscent of the
fluorite structure. The
tCl6sup>2− centers are octahedral. The NH
4+ centers are
hydrogen bond
In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing ...
ed to the
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride s ...
ligands.
[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. ]
Uses and reactions
Ammonium hexachloroplatinate is used in platinum plating. Heating (NH
4)
2 tCl6under a stream of
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
at 200 °C produces
platinum
Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver".
Pla ...
sponge. Treating this with chlorine gives H
2 tCl6[
]
References
{{Platinum compounds
Platinum(IV) compounds
Chloro complexes
Ammonium compounds
Hexachloroplatinates