Potassium tetrachloroplatinate

Potassium tetrachloroplatinate(II) is the chemical compound with the formula K₂PtCl₄. This reddish orange salt is an important reagent for the preparation of other coordination complexes of platinum. It consists of potassium cations and the square planar dianion PtCl₄²⁻. Related salts are also known including Na₂PtCl₄, which is brown-colored and soluble in alcohols, and quaternary ammonium salts, which are soluble in a broader range of organic solvents.

Potassium tetrachloroplatinate

Names
IUPAC name Potassium tetrachloridoplatinate(2–)
Other names Potassium chloroplatinite
Identifiers
CAS Number	10025-99-7
3D model (JSmol)	Interactive image
ChemSpider	55364
ECHA InfoCard	100.030.034
EC Number	233-050-9
PubChem CID	61440≈
UNII	B74O00UCWC
CompTox Dashboard (EPA)	DTXSID10904020
InChI InChI=1S/4ClH.2K.Pt/h4*1H;;;/q;;;;2*+1;+2/p-4 Key: RVRDLMCWUILSAH-UHFFFAOYSA-J InChI=1/4ClH.2K.Pt/h4*1H;;;/q;;;;2*+1;+2/p-4/rCl4Pt.2K/c1-5(2,3)4;;/q-2;2*+1 Key: RVRDLMCWUILSAH-SSOJXQLRAM
SMILES [K+].[K+].Cl[Pt-2](Cl)(Cl)Cl
Properties
Chemical formula	K2PtCl4
Molar mass	415.09 g/mol
Appearance	reddish solid
Density	3.38 g/cm^3
Melting point	265 °C (509 °F; 538 K)
Solubility in water	0.93 g/100 mL (16 °C) 5.3/100 mL (100 °C)
Hazards
EU classification (DSD) (outdated)	Toxic (T) Irritant (Xi)
R-phrases (outdated)	R25, R41, R42, R43
S-phrases (outdated)	S23, S24, S26, S37
NFPA 704 (fire diamond)	0 3 0
Flash point	Non-flammable
Related compounds
Other anions	Potassium hexachloroplatinate
Other cations	Sodium chloroplatinate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation

Potassium tetrachloroplatinate is prepared by reduction of the corresponding hexachloroplatinate salt with sulfur dioxide.[1] K₂PtCl₄ is one of the salts that is most easily obtained from platinum ores. The complex is appreciably soluble only in water. Treatment with alcohols, especially in the presence of base, causes reduction to platinum metal. Organic tetrachloroplatinate salts, such as [PPN]₂PtCl₄ are soluble in chlorocarbons.[2]

Reactions

The chloride ligands on [PtCl₄]²⁻ are displaced by many other ligands. Upon reaction with triphenylphosphine, [PtCl₄]²⁻ converts to cis-bis(triphenylphosphine)platinum chloride:

PtCl₄²⁻ + 2 PPh₃ → cis-PtCl₂(PPh₃)₂ + 2 Cl⁻

The anti-cancer drug Cisplatin can similarly be prepared:[1]

PtCl₄²⁻ + 2 NH₃ → cis-PtCl₂(NH₃)₂ + 2 Cl⁻

Enedithiolates displace all four chloride ligands to give bis(dithiolene) complexes.[3] Reduction gives colloidal platinum of potential interest for catalysis.[4]

Historically, an important reaction involves ammonia and [PtCl₄]²⁻. This reaction affords a deep green precipitate with empirical formula PtCl₂(NH₃)₂. This material, known as Magnus' green salt, is a semiconducting coordination polymer consisting of chains of alternating [PtCl₄]²⁻ and [Pt(NH₃)₄]²⁺ centres.[5]

References

1. Keller, R. N.; Moeller, T. (1963). Potassium Tetrachloroplatinate(II). Inorg. Synth. Inorganic Syntheses. 7. pp. 247–250. doi:10.1002/9780470132333.ch79. ISBN 9780470132333.
2. Elding, L. I.; Oskarsson, A.; Kukushkin, V. Yu (1997). Platinum Complexes Suitable as Precursors for Synthesis in Nonaqueous Solvents. Inorg. Synth. Inorganic Syntheses. 31. pp. 276–279. doi:10.1002/9780470132623.ch47. ISBN 9780470132623.
3. Scott D. Cummings; Richard Eisenberg (1995). "Acid-Base Behavior of the Ground and Excited States of Platinum(II) Complexes of Quinoxaline-2,3-dithiolate". Inorg. Chem. 34 (13): 3396–3403. doi:10.1021/ic00117a005.
4. Ahmadi, T. S.; Wang, Z. L.; Green, T. C.; Henglein, A.; El-Sayed, M. A. (1996). "Shape-Controlled Synthesis of Colloidal Platinum Nanoparticles". Science. 272 (5270): 1924–6. doi:10.1126/science.272.5270.1924. PMID 8662492. S2CID 34481183.
5. Caseri, W. (2004). "Derivatives of Magnus' green salt; from intractable materials to solution-processed transistors". Platinum Metals Review. 48 (3): 91–100. doi:10.1595/147106704X1504.