Platinum(IV) chloride

Platinum(IV) chloride
Identifiers
CAS number	13454-96-1
ChemSpider	19957150
Jmol-3D images	Image 1
SMILES [Pt+2].[Pt+2].[Cl-].[Cl-].[Cl-].[Cl-]
InChI InChI=1/4ClH.2Pt/h4*1H;;/q;;;;2*+2/p-4 Key: KBPRWZWTZAMEIF-XBHQNQODAX
Properties
Molecular formula	PtCl4
Molar mass	336.89 g/mol
Appearance	brown-red powder
Density	4.303 g/cm3 (anhydrous) 2.43 g/cm3 (pentahydrate)
Melting point	370 °C, decomposes
Boiling point	decompose
Solubility in water	dissolves (anhydrous) very soluble (pentahydrate)
Solubility	anhydrous soluble in acetone slightly soluble in ethanol insoluble in ether pentahydrate soluble in alcohol, ether
Hazards
EU classification	not listed
Related compounds
Other anions	platinum(IV) fluoride, platinum disulfide, platinum tetrabromide
Other cations	iridium tetrachloride
Related compounds	platinum(II) chloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Platinum(IV) chloride is the inorganic compound of platinum and chlorine with the empirical formula PtCl₄. This brown solid features platinum in the 4+ oxidation state.

Structure

Typical of Pt(IV), the metal centers adopt an octahedral coordination geometry, {PtCl₆}. This geometry is achieved by forming a polymer wherein half of the chloride ligands bridge between the platinum centers. Because of its polymeric structure, PtCl₄ dissolves only upon breaking the chloride bridging ligands. Thus, addition of HCl give H₂PtCl₆. Lewis base adducts of Pt(IV) of the type cis-PtCl₄L₂ are known, but most are prepared by oxidation of the Pt(II) derivatives.

Part of a (PtCl4)∞ chain from the crystal structure of platinum(IV) chloride

Formation and reactions

PtCl₄ is mainly encountered in the handling of chloroplatinic acid, obtained by dissolving of Pt metal in aqua regia. Heating H₂PtCl₆ gives PtCl₄:

H₂PtCl₆ → PtCl₄ + 2 HCl

If excess acids are removed, PtCl₄ crystallizes from aqueous solutions in large red crystals of pentahydrate PtCl₄·5(H₂O),^[1] which can be dehydrated by heating to about 300 °C in a current of dry chlorine. The pentahydrate is stable and is used as the commercial form of PtCl₄.

Treatment of PtCl₄ with aqueous base gives the [Pt(OH)₆]²⁻ ion. With methyl Grignard reagents followed by partial hydrolysis, PtCl₄ converts to the cuboidal cluster [Pt(CH₃)₃(OH)]₄.^[2] Upon heating PtCl₄ evolves chlorine to give PtCl₂:

PtCl₄ → PtCl₂ + Cl₂

The heavier halides, PtBr₄ and PtI₄, are also known.

References

1. Cotton, S. A. Chemistry of Precious Metals, Chapman and Hall (London): 1997. ISBN 0-7514-0413-6.

1. ^ George Samuel Newth (1920). A text-book of inorganic chemistry. Longmans, Green, and co. p. 694. http://books.google.com/books?id=n6A9AAAAIAAJ. 
2. ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.