Palladium(II) chloride

Last updated
Palladium(II) chloride
Palladium chloride.jpg
Other names
Palladium dichloride, Palladous chloride
3D model (JSmol)
ECHA InfoCard 100.028.724 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 231-596-2
PubChem CID
RTECS number
  • RT3500000
  • InChI=1S/2ClH.Pd/h2*1H;/q;;+2/p-2
  • monomer:Cl[Pd]Cl
  • hexamer:[Cl+]0[Pd-2]12[Cl+][Pd-2]34[Cl+][Pd-2]05[Cl+][Pd-2]6([Cl+]1)[Cl+][Pd-2]([Cl+]2)([Cl+]3)[Cl+][Pd-2]([Cl+]4)([Cl+]5)[Cl+]6
Molar mass 177.326 g/mol (anhydrous)
213.357 g/mol (dihydrate)
Appearancedark red solid
hygroscopic (anhydrous)
dark brown crystals (dihydrate)
Density 4.0 g/cm3
Melting point 679 °C (1,254 °F; 952 K) (decomposes)
soluble in trace amounts, better solubility in cold water
Solubility soluble in organic solvents
dissolves rapidly in HCl
38.0·10−6 cm3/mol
square planar
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
2704 mg/kg (rat, oral)
Related compounds
Other anions
Palladium(II) fluoride
Palladium(II) bromide
Palladium(II) iodide
Other cations
Nickel(II) chloride
Platinum(II) chloride
Platinum(II,IV) chloride
Platinum(IV) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Palladium(II) chloride, also known as palladium dichloride and palladous chloride, are the chemical compounds with the formula PdCl2. PdCl2 is a common starting material in palladium chemistry – palladium-based catalysts are of particular value in organic synthesis. It is prepared by the reaction of chlorine with palladium metal at high temperatures.



Two forms of PdCl2 are known, denoted α and β. In both forms, the palladium centres adopt a square-planar coordination geometry that is characteristic of Pd(II). Furthermore, in both forms, the Pd(II) centers are linked by μ2-chloride bridges. The α-form of PdCl2 is a polymer, consisting of "infinite" slabs or chains. The β-form of PdCl2 is molecular, consisting of an octahedral cluster of six Pd atoms. Each of the twelve edges of this octahedron is spanned by Cl. PtCl2 adopts similar structures, whereas NiCl2 adopts the CdCl2 motif, featuring hexacoordinated Ni(II). [1]

Evolution of b-PdCl2 structure: Start with cubic lattice, remove corner and centered lattice points, inscribe octahedron (red lines), label corners as X (twelve Cl centers) and face-centered atoms as M (six Pd(II) centers). Beta-PdCl2.png
Evolution of β-PdCl2 structure: Start with cubic lattice, remove corner and centered lattice points, inscribe octahedron (red lines), label corners as X (twelve Cl centers) and face-centered atoms as M (six Pd(II) centers).
Alpha-palladium(II)-chloride-xtal-3D-balls.png Pd6Cl12-from-xtal-1996-CM-3D-ellipsoids.png
ball-and-stick model of the
crystal structure of α-PdCl2
thermal ellipsoid model of the Pd6Cl12 molecule
found in the crystal structure of β-PdCl2

Two further polymorphs, γ-PdCl2 and δ-PdCl2, have been reported and show negative thermal expansion. The high-temperature δ form contains planar ribbons of edge-connected PdCl4 squares, like α-PdCl2. The low-temperature γ form has corrugated layers of corner-connected PdCl4 squares. [2]


Palladium(II) chloride is prepared by dissolving palladium metal in aqua regia or hydrochloric acid in the presence of chlorine. Alternatively, it may be prepared by heating palladium sponge metal with chlorine gas at 500 °C. [3] [4] [5] [6]


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 of labile but soluble Lewis base adducts, such as bis(benzonitrile)palladium dichloride and bis(acetonitrile)palladium dichloride. [7] These complexes are prepared by treating PdCl2 with hot solutions of the nitriles:

PdCl2 + 2 RCN → PdCl2(RCN)2

Although occasionally recommended, inert-gas techniques are not necessary if the complex is to be used in situ. As an example, bis(triphenylphosphine)palladium(II) dichloride may be prepared from palladium(II) chloride by reacting it with triphenylphosphine in benzonitrile: [8]

PdCl2 + 2 PPh3 → PdCl2(PPh3)2

Further reduction in the presence of more triphenylphosphine gives tetrakis(triphenylphosphine)palladium(0); the second reaction may be carried out without purifying the intermediate dichloride: [9]

PdCl2(PPh3)2 + 2 PPh3 + 2.5 N2H4 → 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 tetrachloropalladate, by reacting with the appropriate alkali metal chloride in water: [10] 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. [10]

Palladium chloride may also be used to give heterogeneous palladium catalysts: palladium on barium sulfate, palladium on carbon, and palladium chloride on carbon. [11]

A solution of [PdCl4] (aq) Tetrachloropalladate ions in aqueous solution.jpg
A solution of [PdCl4] (aq)


Even when dry, palladium(II) chloride is able to rapidly stain stainless steel. Thus, palladium(II) chloride solutions are sometimes used to test for the corrosion-resistance of stainless steel. [12]

Palladium(II) chloride is sometimes used in carbon monoxide detectors. Carbon monoxide reduces palladium(II) chloride to palladium:

PdCl2 + CO + H2O → Pd + CO2 + 2HCl

Residual PdCl2 is converted to red PdI2, the concentration of which may be determined colorimetrically: [13]

PdCl2 + 2 KI → PdI2 + 2 KCl

Palladium(II) chloride is used in the Wacker process for production of aldehydes and ketones from alkenes.

Palladium(II) chloride can also be used for the cosmetic tattooing of leukomas in the cornea.

Related Research Articles

<span class="mw-page-title-main">Palladium</span> Chemical element, symbol Pd and atomic number 46

Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas. Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). They have similar chemical properties, but palladium has the lowest melting point and is the least dense of them.

<span class="mw-page-title-main">Triphenylphosphine</span> Chemical compound

Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and 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 room temperature. It dissolves in non-polar organic solvents such as benzene and diethyl ether.

<span class="mw-page-title-main">Rhodium(III) chloride</span> Chemical compound

Rhodium(III) chloride refers to inorganic compounds with the formula RhCl3(H2O)n, where n varies from 0 to 3. These are diamagnetic solids featuring octahedral Rh(III) centres. Depending on the value of n, the material is either a dense brown solid or a soluble reddish salt. The soluble trihydrated (n = 3) salt is widely used to prepare compounds used in homogeneous catalysis, notably for the industrial production of acetic acid and hydroformylation.

<span class="mw-page-title-main">Tetrakis(triphenylphosphine)palladium(0)</span> Chemical compound

Tetrakis(triphenylphosphine)palladium(0) (sometimes called quatrotriphenylphosphine palladium) is the chemical compound [Pd(P(C6H5)3)4], often abbreviated Pd(PPh3)4, or rarely PdP4. It is a bright yellow crystalline solid that becomes brown upon decomposition in air.

<span class="mw-page-title-main">Ruthenium(III) chloride</span> Chemical compound

Ruthenium(III) chloride is the chemical compound with the formula RuCl3. "Ruthenium(III) chloride" more commonly refers to the hydrate RuCl3·xH2O. Both the anhydrous and hydrated species are dark brown or black solids. The hydrate, with a varying proportion of water of crystallization, often approximating to a trihydrate, is a commonly used starting material in ruthenium chemistry.

<span class="mw-page-title-main">Tetrakis(triphenylphosphine)platinum(0)</span> Chemical compound

Tetrakis(triphenylphosphine)platinum(0) is the chemical compound with the formula Pt(P(C6H5)3)4, often abbreviated Pt(PPh3)4. The bright yellow compound is used as a precursor to other platinum complexes.

<span class="mw-page-title-main">Bis(triphenylphosphine)iminium chloride</span> Chemical compound

Bis(triphenylphosphine)iminium chloride is the chemical compound with the formula [( 3P)2N]Cl, often abbreviated [(Ph3P)2N]Cl, where Ph is phenyl C6H5, or even abbreviated [PPN]Cl or [PNP]Cl or PPNCl or PNPCl, where PPN or PNP stands for (Ph3P)2N. This colorless salt is a source of the [(Ph3P)2N]+ cation, which is used as an unreactive and weakly coordinating cation to isolate reactive anions. [(Ph3P)2N]+ is a phosphazene.

<span class="mw-page-title-main">Tetraphenylphosphonium chloride</span> Chemical compound

Tetraphenylphosphonium chloride is the chemical compound with the formula (C6H5)4PCl, abbreviated Ph4PCl or PPh4Cl. Tetraphenylphosphonium and especially tetraphenylarsonium salts were formerly of interest in gravimetric analysis of perchlorate and related oxyanions. This colourless salt is used to generate lipophilic salts from inorganic and organometallic anions. Thus, Ph4P+ is useful as a phase-transfer catalyst, again because it allows inorganic anions to dissolve in organic solvents.

<span class="mw-page-title-main">1,1'-Bis(diphenylphosphino)ferrocene</span> Chemical compound

1,1-Bis(diphenylphosphino)ferrocene, commonly abbreviated dppf, is an organophosphorus compound commonly used as a ligand in homogeneous catalysis. It contains a ferrocene moiety in its backbone, and is related to other bridged diphosphines such as 1,2-bis(diphenylphosphino)ethane (dppe).

Martin Arthur Bennett FRS is an Australian inorganic chemist. He gained recognition for studies on the co-ordination chemistry of tertiary phosphines, olefins, and acetylenes, and the relationship of their behaviour to homogeneous catalysis.

<span class="mw-page-title-main">Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium</span> Chemical compound

Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium is the organoruthenium half-sandwich compound with formula RuCl(PPh3)2(C5H5). It as an air-stable orange crystalline solid that is used in a variety of organometallic synthetic and catalytic transformations. The compound has idealized Cs symmetry. It is soluble in chloroform, dichloromethane, and acetone.

<span class="mw-page-title-main">Bis(triphenylphosphine)palladium chloride</span> Chemical compound

Bis(triphenylphosphine)palladium chloride is a coordination compound of palladium containing two triphenylphosphine and two chloride ligands. It is a yellow solid that is soluble in some organic solvents. It is used for palladium-catalyzed coupling reactions, e.g. the Sonogashira–Hagihara reaction. The complex is square planar. Many analogous complexes are known with different phosphine ligands.

<span class="mw-page-title-main">Sodium tetrachloropalladate</span> Chemical compound

Sodium tetrachloropalladate is an inorganic compound with the chemical formula Na2PdCl4. This salt, and the analogous alkali metal salts of the form M2PdCl4, may be prepared simply by reacting palladium(II) chloride with the appropriate alkali metal chloride in aqueous solution. Palladium(II) chloride is insoluble in water, whereas the product dissolves:

<span class="mw-page-title-main">Dichlorotris(triphenylphosphine)ruthenium(II)</span> Chemical compound

Dichlorotris(triphenylphosphine)ruthenium(II) is a coordination complex of ruthenium. It is a chocolate brown solid that is soluble in organic solvents such as benzene. The compound is used as a precursor to other complexes including those used in homogeneous catalysis.

<span class="mw-page-title-main">Metal halides</span>

Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, such as palladium chloride.

<span class="mw-page-title-main">Metal-phosphine complex</span>

A metal-phosphine complex is a coordination complex containing one or more phosphine ligands. Almost always, the phosphine is an organophosphine of the type R3P (R = alkyl, aryl). Metal phosphine complexes are useful in homogeneous catalysis. Prominent examples of metal phosphine complexes include Wilkinson's catalyst (Rh(PPh3)3Cl), Grubbs' catalyst, and tetrakis(triphenylphosphine)palladium(0).

<span class="mw-page-title-main">Rhodium carbonyl chloride</span> Chemical compound

Rhodium carbonyl chloride is an organorhodium compound with the formula Rh2Cl2(CO)4. It is a red-brown volatile solid that is soluble in nonpolar organic solvents. It is a precursor to other rhodium carbonyl complexes, some of which are useful in homogeneous catalysis.

<span class="mw-page-title-main">Bis(benzonitrile)palladium dichloride</span> Chemical compound

Bis(benzonitrile)palladium dichloride is the coordination complex with the formula PdCl2(NCC6H5)2. It is the adduct of two benzonitrile (PhCN) ligands with palladium(II) chloride. It is a yellow-brown solid that is soluble in organic solvents. The compound is a reagent and a precatalyst for reactions that require soluble Pd(II). A closely related compound is bis(acetonitrile)palladium dichloride.

<span class="mw-page-title-main">Transition metal nitrile complexes</span> Class of coordination compounds containing nitrile ligands (coordinating via N)

Transition metal nitrile complexes are coordination compounds containing nitrile ligands. Because nitriles are weakly basic, the nitrile ligands in these complexes are often labile.

<span class="mw-page-title-main">Bis(triphenylphosphine)rhodium carbonyl chloride</span> Chemical compound

Bis(triphenylphosphine)rhodium carbonyl chloride is the organorhodium complex with the formula [RhCl(CO)(PPh3)2]. This complex of rhodium(I) is a bright yellow, air-stable solid. It is the Rh analogue of Vaska's complex, the corresponding iridium complex. With regards to its structure, the complex is square planar with mutually trans triphenylphosphine (PPh3) ligands. The complex is a versatile homogeneous catalyst.


  1. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN   0-12-352651-5.
  2. J. Evers, W. Beck, M. Göbel, S. Jakob, P. Mayer, G. Oehlinger, M. Rotter, T. M. Klapötke (2010). "The Structures of δ-PdCl2 and γ-PdCl2: Phases with Negative Thermal Expansion in One Direction". Angew. Chem. Int. Ed. 49 (33): 5677–5682. doi:10.1002/anie.201000680. PMID   20602377.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. Patnaik, Pradyot (2003). "Palladium". Handbook of inorganic chemicals (1 ed.). New York: McGraw-Hill. p. 687. ISBN   978-0-07-049439-8.
  4. Patnaik, Pradyot (2003). "Palladium Dichloride". Handbook of inorganic chemicals (1 ed.). New York: McGraw-Hill. pp. 688–689. ISBN   978-0-07-049439-8.
  5. Armarego, W. L. F. (2017). "4. Purification of Inorganic and Metal-Organic Chemicals". Purification of laboratory chemicals (Eighth ed.). Amsterdam: Elsevier. p. 687. ISBN   978-0-12-805457-4.
  6. Kharasch, Morris S.; Seyler, Ralph C.; Mayo, Frank R. (1938). "Coördination Compounds of Palladous Chloride". J. Am. Chem. Soc. American Chemical Society. 60 (4): 882–884. doi:10.1021/ja01271a035.
  7. Gordon K. Anderson, Minren Lin (1990). "Bis(Benzonitrile)Dichloro Complexes of Palladium and Platinum". Inorganic Syntheses. Inorg. Synth. Inorganic Syntheses. Vol. 28. pp. 60–63. doi:10.1002/9780470132593.ch13. ISBN   9780470132593.
  8. Norio Miyaura; Akira Suzuki (1993). "Palladium-catalyzed reaction of 1-alkenylboronates with vinylic halides: (1Z,3E)-1-Phenyl-1,3-octadiene". Organic Syntheses .; Collective Volume, vol. 8, p. 532
  9. D. R. Coulson; Satek, L. C.; Grim, S. O. (1972). 23. Tetrakis(triphenylphosphine)palladium(0). Inorg. Synth. Inorganic Syntheses. Vol. 13. pp. 121–124. doi:10.1002/9780470132449.ch23. ISBN   9780470132449.
  10. 1 2 Daniele Choueiry and Ei-ichi Negishi (2002). "II.2.3 Pd(0) and Pd(II) Complexes Containing Phosphorus and Other Group 15 Atom Ligands" (Google Books excerpt). In Ei-ichi Negishi (ed.). Handbook of Organopalladium Chemistry for Organic Synthesis. John Wiley & Sons, Inc. ISBN   0-471-31506-0.
  11. Ralph Mozingo (1955). "Palladium Catalysts". Organic Syntheses .; Collective Volume, vol. 3, p. 685
  12. For example,
  13. T. H. Allen, W. S. Root (1955). "Colorimetric Determination of Carbon Monoxide in Air by an improved Palladium Chloride Method". J. Biol. Chem. 216 (1): 309–317. doi: 10.1016/S0021-9258(19)52307-9 . PMID   13252030.