Platinum(IV) chloride is the inorganic compound of platinum and chlorine with the empirical formula PtCl<sub>4</sub>. This brown solid features platinum in the +4 oxidation state.
Typical of Pt(IV), the metal centers adopt an octahedral coordination geometry, {PtCl<sub>6</sub>}. This geometry is achieved by forming a polymer wherein half of the chloride ligands bridge between the platinum centers. Because of its polymeric structure, PtCl<sub>4</sub> dissolves only upon breaking the chloride bridging ligands. Thus, addition of HCl give H<sub>2</sub>PtCl<sub>6</sub>. Lewis base adducts of Pt(IV) of the type cis-PtCl<sub>4</sub>L<sub>2</sub> are known, but most are prepared by oxidation of the Pt(II) derivatives.
PtCl<sub>4</sub> is mainly encountered in the handling of chloroplatinic acid, obtained by dissolving of Pt metal in aqua regia. Heating H<sub>2</sub>PtCl<sub>6</sub> to 220 ðC gives impure PtCl<sub>4</sub>:
A purer product can be produced by heating under chlorine gas at 250 ðC.
If excess acids are removed, PtCl<sub>4</sub> crystallizes from aqueous solutions in large red crystals of pentahydrate PtCl<sub>4</sub>÷5(H<sub>2</sub>O), which can be dehydrated by heating to about 300 ðC in a current of dry chlorine. The pentahydrate is stable and is used as the commercial form of PtCl<sub>4</sub>.
Treatment of PtCl<sub>4</sub> with aqueous base gives the [Pt(OH)<sub>6</sub>]<sup>2âÂÂ</sup> ion. With methyl Grignard reagents followed by partial hydrolysis, PtCl<sub>4</sub> converts to the cuboidal cluster [Pt(CH<sub>3</sub>)<sub>3</sub>(OH)]<sub>4</sub>. Upon heating PtCl<sub>4</sub> evolves chlorine to give PtCl<sub>2</sub>:
The heavier halides, PtBr<sub>4</sub> and PtI<sub>4</sub>, are also known.