Platinum(II) chloride is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

Pt Cl₂. 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 Diamagnetic materials are repelled by a magnetic field; an applied magnetic field creates an induced magnetic field in them in the opposite direction, causing a repulsive force. In contrast, paramagnetic and ferromagnetic materials are attracted ...

, 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

ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elect ...

s. Complementarily, each Cl center is two-coordinate, being connected to two platinum atoms. The structure of α-PtCl₂ is reported to be disordered and contain edge- and/or corner-sharing square-planar PtCl₄ units. Beta-PdCl2

Preparation

β-PtCl₂ is prepared by heating chloroplatinic acid to 350 °C in air. : 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 Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...

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: :PtCl₄ → PtCl₂ + Cl₂ Transformations such as this are "driven" by

entropy Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodyna ...

, 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 Gravimetry is the measurement of the strength of a gravitational field. Gravimetry may be used when either the magnitude of a gravitational field or the properties of matter responsible for its creation are of interest. Units of measurement G ...

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, t(NH₃)₄PtCl₄]. Of the many such complex (chemistry), complexes that have been described, the following are illustrative:Cotton, S. A. ''Chemistry of Precious Metals'', Chapman and Hall (London): 1997. *pink K₂PtCl₄, a widely employed water-soluble derivative. *colorless ''cis''-PtCl₂(NH₃)₂, better known as

cisplatin Cisplatin is a chemotherapy medication used to treat a number of cancers. These include testicular cancer, ovarian cancer, cervical cancer, breast cancer, bladder cancer, head and neck cancer, esophageal cancer, lung cancer, mesothelioma, ...

. *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 In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Is ...

. *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 chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysi ...

in the service of

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

or as anti-cancer drugs.

References

{{Chlorides Chlorides Chlorides,2 Platinum group halides

Structure

Preparation

Uses

See also

References