View source for Platinum(II) chloride

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 464208503
| Name = Platinum(II) chloride
| ImageFile = Platinum(II) chloride.jpg
| ImageFile2 = Beta-platinum(II)-chloride-from-xtal-3D-balls-A.png
| ImageName2 = Ball-and-stick model of a Pt6Cl12 molecule in the beta polymorph of platinum(II) chloride
| IUPACName = Platinum(II) chloride
| OtherNames = Platinous chloride
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|changed|??}}
| CASNo = 10025-65-7
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 49801
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 2668
| EC_number = 233-034-1
| Gmelin = 1744965
| PubChem = 2770
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 896SQ4TDHW
| InChI = 1/2ClH.Pt/h2*1H;/q;;+2/p-2
| InChIKey = CLSUSRZJUQMOHH-NUQVWONBAP
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/2ClH.Pt/h2*1H;/q;;+2/p-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = CLSUSRZJUQMOHH-UHFFFAOYSA-L
| SMILES = Cl[Pt]Cl
| SMILES_Comment = monomer
| SMILES1 = [Cl+]0[Pt-2]12[Cl+][Pt-2]34[Cl+][Pt-2]05[Cl+][Pt-2]6([Cl+]1)[Cl+][Pt-2]([Cl+]2)([Cl+]3)[Cl+][Pt-2]([Cl+]4)([Cl+]5)[Cl+]6
| SMILES1_Comment = hexamer
 }}
|Section2={{Chembox Properties
| Formula = [[Platinum|Pt]][[Chlorine|Cl]]<sub>2</sub>
| Appearance = dark brown powder
| MolarMass = 265.99&nbsp;g/mol
| Density = 6.05&nbsp;g/cm<sup>3</sup>, solid
| Solubility = insoluble
| SolubleOther = insoluble in [[ethanol|alcohol]], [[diethyl ether|ether]] <br> soluble in [[hydrochloric acid|HCl]], [[ammonia]]
| MeltingPtC = 581
| BoilingPt = decomposes
| MagSus = &minus;54.0·10<sup>−6</sup> cm<sup>3</sup>/mol
  }}
|Section3={{Chembox Structure
| CrystalStruct = hexagonal
  }}
|Section7={{Chembox Hazards
| GHS_ref=<ref>{{cite web |title=Platinum(II) chloride |url=https://pubchem.ncbi.nlm.nih.gov/compound/2770#section=Safety-and-Hazards |website=pubchem.ncbi.nlm.nih.gov |access-date=27 December 2021 |language=en}}</ref>
| GHSPictograms = {{GHS05}}{{GHS07}}{{GHS08}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|314|315|317|319|334}}
| PPhrases = {{P-phrases|260|261|264|272|280|285|301+330+331|302+352|303+361+353|304+340|304+341|305+351+338|310|321|332+313|333+313|337+313|342+311|362|363|405|501}}
| LD50 = 3423&nbsp;mg/kg (rat, oral)
  }}
|Section8={{Chembox Related
| OtherAnions = [[Platinum(II) bromide]] <br/> [[Platinum(II) sulfide]]
| OtherCations = [[Palladium(II) chloride]]
| OtherCompounds = [[Platinum(IV) chloride]]
  }}
}}

'''Platinum(II) chloride''' describes the [[inorganic compound]]s with the formula [[Platinum|Pt]][[Chlorine|Cl<sub>2</sub>]]. They are precursor used in the preparation of other platinum compounds. Platinum(II) chloride exists in two crystalline forms ([[crystal polymorphism|polymorphs]]), but the main properties are somewhat similar: dark brown, insoluble in water, [[diamagnetism|diamagnetic]], and odorless.

==Structure==
The structures of PtCl<sub>2</sub> and [[palladium(II) chloride|PdCl<sub>2</sub>]] are similar. These dichlorides exist in both polymeric, or "α", and hexameric, or "β" structures. The β form converts to the α form at 500&nbsp;°C. In the β form, the Pt-Pt distances are 3.32–3.40&nbsp;Å, indicative of some bonding between the pairs of metals. In both forms of PtCl<sub>2</sub>, each Pt center is four-coordinate, being surrounded by four chloride [[ligand]]s. Complementarily, each Cl center is two-coordinate, being connected to two platinum atoms.<ref>Holleman, A. F.; Wiberg, E. ''Inorganic Chemistry'' Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}.</ref> The structure of α-PtCl<sub>2</sub> is reported to be disordered and contain edge- and/or corner-sharing square-planar PtCl<sub>4</sub> units.<ref>{{ cite journal | first1 = Bernt | last1 = Krebs | first2 = Claus | last2 = Brendel | first3 = Harald | last3 = Schäfer | title = Neue Untersuchungen an α-Platindichlorid Darstellung und Struktur | journal = [[Zeitschrift für anorganische und allgemeine Chemie|Z. Anorg. Allg. Chem.]] | year = 1988 | volume = 561 | issue = 1 | pages = 119–131 | doi = 10.1002/zaac.19885610113 }}</ref>

[[File:Beta-PdCl2.png|thumb|400px|Evolution of β-PtCl<sub>2</sub> structure: Start with cubic lattice, remove corner and centered lattice points, inscribe octahedron (red lines), label corners as X (twelve Cl<sup>−</sup> centers) and face-centered atoms as M (six Pt(II) centers).]]

==Preparation==
β-PtCl<sub>2</sub> is prepared by heating [[chloroplatinic acid]] to 350&nbsp;°C in air.<ref>{{cite book | author1 = Kerr, G. T. | author2 = Schweizer, A. E. | title = Inorganic Syntheses | chapter = β-Platinum(II) Chloride | journal = [[Inorg. Synth.]] | volume = 20 | pages = [https://archive.org/details/inorganicsynthes0000unse/page/48 48–49] | doi = 10.1002/9780470132517.ch14 | date = 2007 | isbn = 978-0-470-13251-7 | chapter-url = https://archive.org/details/inorganicsynthes0000unse/page/48 }}</ref>

:[[chloroplatinic acid|H<sub>2</sub>PtCl<sub>6</sub>]] → PtCl<sub>2</sub> + Cl<sub>2</sub> + 2 HCl

This method is convenient since the chloroplatinic acid is generated readily from Pt metal. Aqueous solutions of H<sub>2</sub>PtCl<sub>6</sub> can also be reduced with [[hydrazine|hydrazinium]] salts, but this method is more laborious than the thermal route of Kerr and Schweizer.

Although PtCl<sub>2</sub> can form when platinum metal contacts hot [[chlorine]] gas, this process suffers from over-chlorination to give [[platinum(IV) chloride|PtCl<sub>4</sub>]]. [[Jöns Jakob Berzelius|Berzelius]] and later Wöhler and Streicher showed that upon heating to 450&nbsp;°C, this Pt(IV) compound decomposes to the Pt(II) derivative:<ref>{{cite journal |author1=Wöhler, L. |author2=Streicher, S. | journal = [[Chem. Ber.]] | title = Über das Beständigkeitsgebiet von vier wasserfreien Platinchloriden, über die Flüchtigkeit des Metalls im Chlorgas und die Darstellung sauerstoff-freien Chlors | year = 1913 | volume = 46 | pages = 1591–1597 | doi = 10.1002/cber.19130460252 | issue = 2|url=https://zenodo.org/record/1426521 }}</ref><ref name="decomp">{{cite journal |author1=A. E. Schweizer |author2=G. T. Kerr |title=Thermal decomposition of hexachloroplatinic acid |journal=Inorganic Chemistry |date=1978 |volume=17 |issue=8 |pages=2326–2327 |doi=10.1021/ic50186a067 |language=en}}</ref>

:PtCl<sub>4</sub> → PtCl<sub>2</sub> + Cl<sub>2</sub>

Transformations such as this are "driven" by [[entropy]], the free energy gained upon the release of a gaseous product from a solid. Upon heating to still higher temperatures, PtCl<sub>2</sub> releases more chlorine to give metallic Pt. This conversion is the basis of the [[gravimetric]] assay of the purity of the PtCl<sub>2</sub> product.

==Reactions==
Most reactions of PtCl<sub>2</sub> proceed via treatment with ligands (L) to give molecular derivatives. These transformations entail depolymerization via cleavage of Pt-Cl-Pt linkages:
:PtCl<sub>2</sub> + 2 L → PtCl<sub>2</sub>L<sub>2</sub>
Addition of ammonia gives initially "PtCl<sub>2</sub>(NH<sub>3</sub>)<sub>2</sub>", "[[Magnus's green salt]]", also described as [Pt(NH<sub>3</sub>)<sub>4</sub>][PtCl<sub>4</sub>].

Many [[complex (chemistry)|complexes]] have been described, the following are illustrative:<ref>Cotton, S. A. ''Chemistry of Precious Metals'', Chapman and Hall (London): 1997. {{ISBN|0-7514-0413-6}}</ref>
*pink K<sub>2</sub>PtCl<sub>4</sub>, a widely employed water-soluble derivative.
*colorless ''cis''-PtCl<sub>2</sub>(NH<sub>3</sub>)<sub>2</sub>, better known as [[cisplatin]].
*colorless [[Bis(triphenylphosphine)platinum chloride|''cis''-PtCl<sub>2</sub>(P(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>)<sub>2</sub>]], a common precursor to other complexes of the type PtX(Cl)(P(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>)<sub>2</sub> (X = H, CH<sub>3</sub>, etc.).
*yellow ''trans''-PtCl<sub>2</sub>(P(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>)<sub>2</sub>, a metastable relative of the ''cis''- [[isomer]].
*colorless [[dichloro(cycloocta-1,5-diene)platinum(II)]] (Pt(cod)Cl<sub>2</sub>), an "organic-soluble" compound containing a labile organic ligand.

Several of these compounds are of interest in [[homogeneous catalysis]] in the service of [[organic synthesis]] or as anti-cancer drugs.

==See also==
* [[Platinum(IV) chloride]]

==References==
{{reflist}}
{{Platinum compounds}}
{{Chlorides}}

[[Category:Chlorides]]
[[Category:Platinum(II) compounds|Chlorides,2]]
[[Category:Platinum group halides]]