2PtCl6.svg) | |
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| Names | |
|---|---|
| IUPAC name Dihydronium hexachloroplatinate(2–) | |
| Other names Hexachloroplatinic acid Hydronium hexachloroplatinate(IV) | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.037.267 |
| EC Number |
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| RTECS number |
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| UNII | |
| UN number | 2507 |
| |
| |
| Properties | |
| H2Cl6Pt | |
| Molar mass | 409.81 g/mol |
| Appearance | Reddish brown solid |
| Density | 2.431 g/cm3 |
| Melting point | 60 °C (140 °F; 333 K) |
| Boiling point | decomposes |
| highly soluble | |
| Structure | |
| anti-fluorite | |
| octahedral | |
| 0D | |
| Hazards | |
| GHS labelling: | |
    | |
| Danger | |
| H301,H314,H317,H334 | |
| P260,P264,P270,P272,P280,P285,P301+P310,P301+P330+P331,P302+P352,P303+P361+P353,P304+P340,P304+P341,P305+P351+P338,P310,P321,P330,P333+P313,P342+P311,P363,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Safety data sheet (SDS) | External MSDS |
| Related compounds | |
Otheranions | Hexachloropalladic acid, Hexachloroosmic acid |
Othercations | Potassium hexachloroplatinate, Ammonium hexachloroplatinate, Rubidium hexachloroplatinate, Caesium hexachloroplatinate |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Chloroplatinic acid (also known ashexachloroplatinic acid) is aninorganic compound with the formula [H3O]2[PtCl6](H2O)x (0 ≤x ≤ 6). A red solid, it is an important commercial source ofplatinum, usually as anaqueous solution. Although often written in shorthand as H2PtCl6, it is thehydronium (H3O+) salt of the hexachloroplatinate anion (PtCl2−
6).[1][2][3] Hexachloroplatinic acid is highlyhygroscopic.
Hexachloroplatinic acid may be produced via a variety of methods. The most common of these methods involves dissolution of platinum inaqua regia. Other methods include exposing an aqueous suspension of platinum particles to chlorine gas, or via electrolysis.
When produced by the aqua regia route, hexachloroplatinic acid is thought to arise by the following equation:[4][5]
The resulting orange/red solution can be evaporated to produce brownish red crystals. Some authors suggest that hexachloroplatinic acid produced using this method is contaminated with nitrosonium hexachloroplatinate. Newer literature indicates that this is not the case, and that once the nitric acid has been driven off, samples prepared via this method contain no detectable nitrogen.[weasel words]
Alternative methods have been investigated and described, often motivated by the avoidance of nitrogen contamination.[6]
According toX-ray crystallography, hexachloroplatinic acid consists of octahedral PtCl2−
6 ions linked by hydrogen bonding. The cubic array of these octahedra encase water molecules.[7]
When heated, hexachloroplatinic acid decomposes toplatinum(IV) chloride.[1]
Chloroplatinic acid was popularized for thequantitative analysis of potassium. The potassium is selectively precipitated fromsolution as potassium hexachloroplatinate. Determinations were done in 85% (v/v) alcohol solutions with excess platinate ions, and the precipitated product was weighed. Potassium could be detected for solutions as dilute as 0.02 to 0.2% (m/v).[8]
This method for determination of potassium was advantageous compared to thesodium cobaltinitrite method used previously, since it required a singleprecipitation reaction.[8]Gravimetric analysis of precipitated products has been supplanted by moderninstrumental analysis methods such asion selective electrodes,flame photometry,ICP-AES orICP-MS.
Upon treatment with an ammonium salt, such asammonium chloride, chloroplatinic acid converts toammonium hexachloroplatinate, which precipitates as a solid.[4] Upon heating in an atmosphere ofhydrogen, the ammonium salt converts to elemental platinum. Platinum is often isolated from ores or recycled from residues using this method.[9]
Like many platinum compounds, chloroplatinic acid is a catalyst (or precatalyst) forhydrogenation and related reactions. As first reported by John Speier and colleagues fromDow Corning, it catalyzes the addition of hydrosilanes to olefins, i.e.hydrosilylation. Early demonstration reactions used isopropanol solutions oftrichlorosilane (SiHCl3) withpentenes. Prior work on the addition of silanes to alkenes required radical reactions that were inefficient.[10][11] As well as withKarstedt's catalyst, Speier's catalyst enjoys widespread use for hydrosilylation, the main drawback is the deliquescent properties of the catalyst.[12]
It is generally agreed that chloroplatinic acid is a precursor to the actual catalyst. A possible role for colloidal platinum orzero-valent complexes has also been considered.[13]
Chloroplatinic acid prepared fromaqua regia is proposed to contain nitrosonium hexachloroplatinate, (NO)2PtCl6. Nitrosonium hexachloroplatinate is obtained by the reaction ofnitrosyl chloride (NOCl) and platinum metal.[14] Nitrosonium hexachloroplatinate has been found to react vigorously with water and hydrochloric acid, making contamination of chloroplatinic acid prepared with aqua regia with nitrosonium hexachloroplatinate unlikely.[citation needed]
