Palladium(II) chloride, also known as
palladium dichloride, are the
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
s with the
formulaA chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
PdCl
2. PdCl
2 is a common starting material in
palladiumPalladium is a chemical element with the chemical symbol Pd and an atomic number of 46. Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it after the asteroid Pallas, which in turn, was named after the epithet of the Greek...
chemistry – palladium-based catalysts are of particular value in
organic synthesisOrganic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
. It is prepared by
chlorinationChlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water...
of
palladiumPalladium is a chemical element with the chemical symbol Pd and an atomic number of 46. Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it after the asteroid Pallas, which in turn, was named after the epithet of the Greek...
.
Two forms of PdCl
2 are known. In both forms, the palladium centres adopt the square-planar coordination geometry that is characteristic of Pd(II).
Palladium(II) chloride, also known as
palladium dichloride, are the
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
s with the
formulaA chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
PdCl
2. PdCl
2 is a common starting material in
palladiumPalladium is a chemical element with the chemical symbol Pd and an atomic number of 46. Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it after the asteroid Pallas, which in turn, was named after the epithet of the Greek...
chemistry – palladium-based catalysts are of particular value in
organic synthesisOrganic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
. It is prepared by
chlorinationChlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water...
of
palladiumPalladium is a chemical element with the chemical symbol Pd and an atomic number of 46. Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it after the asteroid Pallas, which in turn, was named after the epithet of the Greek...
.
Structure
Two forms of PdCl
2 are known. In both forms, the palladium centres adopt the square-planar coordination geometry that is characteristic of Pd(II). Furthermore, in both forms, the Pd(II) centres are linked by μ
2-chloride
bridgeA bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually restricted to small ligands such as pseudohalides or to ligands that are...
s. The α-form of PdCl
2 is a polymer, consisting of "infinite" slabs or chains. The β-form of PdCl
2 is molecular, consisting of an
octahedral clusterOctahedral clusters are inorganic or organometallic cluster compounds composed of six metals in an octahedral array. One important class of octahedral clusters are chalcohalide clusters of the type M6X8L6 where M is a metal usually of group 6 or group 7, X is a...
of six Pd atoms. Each of the twelve edges of this octahedron is spanned by Cl
-. PtCl
2 adopts similar structures, whereas NiCl
2 adopts the CdCl
2 motif, featuring hexacoordinated Ni(II).
Reactions
Palladium(II) chloride is a common starting point in the synthesis of other palladium compounds. It is not particularly soluble in water or non-coordinating solvents, so the first step in its utilization is often the preparation labile but soluble Lewis base
adductAn adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components, with formation of two chemical bonds and a net reduction in bond multiplicity in at least one of the reactants. The resultant is considered...
s, such as those derived from
acetonitrileAcetonitrile is the chemical compound with formula CH3CN. This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture. It is widely used as a polar aprotic solvent in synthetic chemistry, and as a medium-polarity solvent in...
or
benzonitrileBenzonitrile is the chemical compound with the formula C6H5CN, abbreviated PhCN. This aromatic organic compound is colourless, with a sweet almond odour. It is prepared by the dehydration of benzamide, or by the reaction of sodium cyanide with...
.
The acetonitrile complex is prepared by treating PdCl
2 in refluxing acetonitrile:
- PdCl2 + 2 MeCN → PdCl2(MeCN)2
Although occasionally recommended,
inert-gas techniquesAir-free techniques refer to a range of manipulations in the chemistry laboratory for the handling of compounds that are air-sensitive. These techniques prevent the compounds from reacting with components of air, usually water and oxygen; less commonly carbon dioxide and nitrogen...
are not necessary if the complex is to be used
in situ. As an example,
bis(triphenylphosphine)palladium(II) dichlorideBispalladium dichloride is a coordination compound of palladium containing two triphenylphosphine and two chloride ligands. This yellow complex is often used for palladium-catalyzed coupling reactions, e.g. the Sonogashira–Hagihara reaction...
may be prepared from palladium(II) chloride by reacting it with
triphenylphosphineTriphenylphosphine is a common organophosphorus compound with the formula P3 - often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at...
in benzonitrile:
- PdCl2 + 2 PPh3 → PdCl2(PPh3)2
Further reduction in the presence of more triphenylphosphine gives
tetrakis(triphenylphosphine)palladium(0)Tetrakispalladium is the chemical compound Pd[P3]4, often abbreviated Pd4, or even PdP4...
; the second reaction may be carried out without purifying the intermediate dichloride:
- PdCl2(PPh3)2 + 2 PPh3 + 2.5 N2H4
Hydrazine is an inorganic chemical compound with the formula N2H4. It is a colourless liquid with an ammonia-like odor and is derived from the same industrial chemistry processes that manufacture ammonia...
→ Pd(PPh3)4 + 0.5 N2 + 2 N2H5+Cl-
Alternatively, palladium(II) chloride may be solubilized in the form of the tetrachloropalladate anion, e.g.
sodium tetrachloropalladateSodium tetrachloropalladate is an inorganic compound. This salt, and the analogous alkali metal salts of the form M2PdCl4 may be prepared simply by reacting palladium chloride with the appropriate alkali metal chloride in aqueous solution...
, by reacting with the appropriate alkali metal chloride in water: Palladium(II) chloride is insoluble in water, whereas the product dissolves:
- PdCl2 + 2 MCl → M2PdCl4
This compound may also further react with phosphines to give phosphine complexes of palladium.
Uses
Even when dry, palladium(II) chloride is able to rapidly stain
stainless steelIn metallurgy, stainless steel, also known as inox steel or inox, is defined as a steel alloy with a minimum of 11% chromium content by mass. Stainless steel does not stain, corrode, or rust as easily as ordinary steel...
. Thus, palladium(II) chloride solutions are sometimes used to test for the
corrosionCorrosion is the disintegration of a material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means a loss of electrons of metals reacting with water and oxygen. Weakening of iron due to oxidation of the iron atoms is a...
-resistance of stainless steel. Palladium(II) chloride is sometimes used in
carbon monoxideCarbon monoxide is a colorless, odorless and tasteless gas, yet very toxic to humans. It consists of one carbon atom and one oxygen atom, connected by a covalent double bond and a dative covalent bond...
detectors.
Safety
The related
nickelNickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature, other three being iron, cobalt and gadolinium...
and
platinumPlatinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements...
compounds are known to be
irritantIrritant may refer to:* Something that causes irritation.* Irritant , a psychedelic trance album* Irritant , a United Kingdom rock musical group* Irritant , a stimulus or agent which induces the state of irritation...
s of the skin and the respiratory system and, in some cases,
carcinogenA carcinogen is any substance, radionuclide or radiation that is an agent directly involved in the promotion of cancer or in the increase of its propagation. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
ic, and its is generally accepted as prudent to assume that palladium compounds share these risks.