“Platinum(II) chloride”的意思、由来-开放百科全书

词条

Platinum(II) chloride

释义

Structure
Preparation
Uses
See also
References

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 464208503
| Name = Platinum(II) chloride
| ImageFile1 = File:PtCl2.jpg
| ImageName1 = Photograph of an orange, powdery sample of platinum(II) chloride
| 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
| OtherNames = Platinous chloride
|Section1={{Chembox Identifiers
| InChI = 1/2ClH.Pt/h2*1H;/q;;+2/p-2
| InChIKey = CLSUSRZJUQMOHH-NUQVWONBAP
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 49801
| 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
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/2ClH.Pt/h2*1H;/q;;+2/p-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = CLSUSRZJUQMOHH-UHFFFAOYSA-L
| CASNo_Ref = {{cascite|changed|??}}
| CASNo = 10025-65-7
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII = 896SQ4TDHW
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 2668
| PubChem = 2770
|Section2={{Chembox Properties
| Formula = PtCl₂
| Appearance = olive green crystals
| MolarMass = 265.99 g/mol
| Density = 6.05 g/cm³, solid
| Solubility = insoluble
| SolubleOther = insoluble in alcohol, ether
soluble in HCl, ammonia
| MeltingPtC = 581
| BoilingPt = decomposes
| MagSus = −54.0·10⁻⁶ cm³/mol
|Section3={{Chembox Structure
| CrystalStruct = hexagonal
|Section7={{Chembox Hazards
| EUClass = not listed
| LD50 = 3423 mg/kg (rat, oral)
|Section8={{Chembox Related
| OtherAnions = platinum(II) sulfide, platinum(II) iodide
| OtherCations = palladium(II) chloride, iridium dichloride
| OtherCompounds = platinum trichloride
}}

Platinum(II) chloride is the chemical compound PtCl₂. It is an important precursor used in the preparation of other platinum compounds. It exists in two crystalline forms, but the main properties are somewhat similar: dark brown, insoluble in water, diamagnetic, and odorless.

Structure

The structures of PtCl₂ and PdCl₂ 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 °C. In the β form, the Pt-Pt distances are 3.32–3.40 Å, indicative of some bonding between the pairs of metals. In both forms of PtCl₂, each Pt center is four-coordinate, being surrounded by four chloride ligands. Complementarily, each Cl center is two-coordinate, being connected to two platinum atoms.^[1]

Preparation

β-PtCl₂ is prepared by heating chloroplatinic acid to 350 °C in air.^[2]

H₂PtCl₆ → PtCl₂ + Cl₂ + 2 HCl

This method is convenient since the chloroplatinic acid is generated readily from Pt metal. Aqueous solutions of H₂PtCl₆ can also be reduced with hydrazinium salts, but this method is more laborious than the thermal route of Kerr and Schweizer.

Although PtCl₂ must form when platinum metal contacts hot chlorine gas, this process suffers from over-chlorination to give PtCl₄. Berzelius and later Wöhler and Streicher showed that upon heating to 450 °C, this Pt(IV) compound decomposes to the Pt(II) derivative:^[3]

PtCl₄ → PtCl₂ + Cl₂

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, PtCl₂ releases more chlorine to give metallic Pt. This conversion is the basis of the gravimetric assay of the purity of the PtCl₂ product.

Uses

Most reactions of PtCl₂ proceed via treatment with ligands (L) to give molecular derivatives. These transformations entail depolymerization via cleavage of Pt-Cl-Pt linkages:

PtCl₂ + 2 L → PtCl₂L₂

Sometimes, such reactions can be deceptive. Addition of ammonia gives initially "PtCl₂(NH₃)₂", but this material is in fact Magnus's green salt, [PtCl₄][Pt(NH₃)₄].

Of the many such complexes that have been described, the following are illustrative:^[4]

pink K₂PtCl₄, a widely employed water-soluble derivative.
colorless cis-PtCl₂(NH₃)₂, better known as cisplatin.
colorless cis-PtCl₂(P(C₆H₅)₃)₂, a commonly employed, easily crystallized species that is widely employed as a precursor other complexes of the type PtX(Cl)(P(C₆H₅)₃)₂ (X = H, CH₃, etc.).
yellow trans-PtCl₂(P(C₆H₅)₃)₂, a metastable relative of the cis- isomer.
colorless dichloro(cycloocta-1,5-diene)platinum(II) (Pt(cod)Cl₂), 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.

References

1. ^Holleman, A. F.; Wiberg, E. Inorganic Chemistry Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}.
2. ^{{cite journal |author1=Kerr, G. T. |author2=Schweizer, A. E. | journal =Inorg. Synth. | year = 1980 | volume = 20 | pages = 48–49 | doi = 10.1002/9780470132517.ch14 | title = β-Platinum(II) Chloride | series = Inorganic Syntheses | isbn = 978-0-470-13251-7}}
3. ^{{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}}
4. ^Cotton, S. A. Chemistry of Precious Metals, Chapman and Hall (London): 1997. {{ISBN|0-7514-0413-6}}

3 : Chlorides|Platinum(II) compounds|Metal halides

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Structure

Preparation

Uses

See also

References