Palladium(II) chloride: Difference between revisions

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 431915305

| Name = Palladium(II) chloride

| ImageFile = Palladium chloride.jpg

| ImageName = Palladium(II) chloride<br/>Palladium dichloride

| ImageFile2 = Palladium(II)-chloride-3D-vdW.png

| ImageFile3 = Palladium(II)-chloride-3D-balls.png

| OtherNames = Palladium dichloride, Palladous chloride

|Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo = 7647-10-1

| UNII_Ref = {{fdacite|changed|FDA}}

| UNII = N9214IR8N7

| EINECS = 231-596-2

| RTECS = RT3500000

| PubChem = 24290

| SMILES = Cl[Pd]Cl

| SMILES_Comment = monomer

| SMILES1 = [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

| SMILES1_Comment = hexamer

| InChI = 1S/2ClH.Pd/h2*1H;/q;;+2/p-2

| InChIKey = PIBWKRNGBLPSSY-UHFFFAOYSA-L

| ChemSpiderID = 22710

|Section2={{Chembox Properties

| Formula = PdCl₂

| MolarMass = 177.326 g/mol (anhydrous) <br> 213.357 g/mol (dihydrate)

| Appearance = dark red solid <br> [[hygroscopic]] (anhydrous) <br> dark brown crystals (dihydrate)

| Density = 4.0 g/cm³

| Solubility = soluble in trace amounts, better solubility in cold water

| SolubleOther = soluble in [[organic solvents]] <br> dissolves rapidly in [[hydrochloric acid|HCl]]

| MeltingPtC = 679

| MeltingPt_notes = (decomposes)

| MagSus = {{val|-38.0e-6}} cm³/mol

|Section3={{Chembox Structure

| Coordination = square planar

| CrystalStruct = rhombohedral

|Section4={{Chembox Thermochemistry

| DeltaHf =

| Entropy =

|Section7={{Chembox Hazards

| ExternalSDS =

| MainHazards =

| NFPA-H =

| NFPA-F =

| NFPA-R =

| NFPA-S =

| HPhrases = {{HPhrases|}}

| PPhrases = {{PPhrases|}}

| GHS_ref =

| FlashPt = Non-flammable

| PEL =

| LD50 = 2704 mg/kg (rat, oral)

|Section8={{Chembox Related

| OtherAnions = [[Palladium(II) fluoride]]<br/>[[Palladium(II) bromide]]<br/>[[Palladium(II) iodide]]

| OtherCations = [[Nickel(II) chloride]]<br/>[[Platinum(II) chloride]]<br/>[[Platinum(II,IV) chloride]]<br/>[[Platinum(IV) chloride]]

'''Palladium(II) chloride''', also known as '''palladium dichloride''' and '''palladous chloride''', are the [[chemical compound]]s with the [[chemical formula|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 [[bridging ligand|bridge]]s. 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⁻. [[Platinum(II) chloride|PtCl₂]] adopts similar structures, whereas [[Nickel(II) chloride|NiCl₂]] adopts the [[Cadmium chloride|CdCl₂]] motif, featuring hexacoordinated Ni(II).<ref>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}.</ref>

[[Image:Beta-PdCl2.png|thumb|left|400px|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).]]

{| class="wikitable" style="margin:1em auto; text-align:center;"

|[[File:Alpha-palladium(II)-chloride-xtal-3D-balls.png|250px]]||[[File:Pd6Cl12-from-xtal-1996-CM-3D-ellipsoids.png|150px]]

|<small>[[ball-and-stick model]] of the<br />crystal structure of α-PdCl₂</small>||<small>[[thermal ellipsoid]] model of the Pd₆Cl₁₂ molecule<br />found in the crystal structure of β-PdCl₂</small>

Two further [[Polymorphism (materials science)|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.<ref>{{cite journal | author = J. Evers, W. Beck, M. Göbel, S. Jakob, P. Mayer, G. Oehlinger, M. Rotter, [[Thomas M. Klapötke|T. M. Klapötke]] | title = The Structures of δ-PdCl₂ and γ-PdCl₂: Phases with Negative Thermal Expansion in One Direction | doi = 10.1002/anie.201000680 | journal = [[Angewandte Chemie|Angew. Chem. Int. Ed.]] | year = 2010 | volume = 49 | pages = 5677–5682 | issue = 33 | pmid = 20602377 }}</ref>

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&nbsp;°C.<ref>{{cite book |last1=Patnaik |first1=Pradyot |title=Handbook of inorganic chemicals |date=2003 |publisher=McGraw-Hill |location=New York |isbn=978-0-07-049439-8 |page=687 |edition=1 |chapter=Palladium}}</ref><ref>{{cite book |last1=Patnaik |first1=Pradyot |title=Handbook of inorganic chemicals |date=2003 |publisher=McGraw-Hill |location=New York |isbn=978-0-07-049439-8 |pages=688–689 |edition=1 |chapter=Palladium Dichloride}}</ref><ref>{{cite book |last1=Armarego |first1=W. L. F. |title=Purification of laboratory chemicals |date=2017 |publisher=Elsevier |location=Amsterdam |isbn=978-0-12-805457-4 |page=687 |edition=Eighth |chapter=4. Purification of Inorganic and Metal-Organic Chemicals}}</ref><ref>{{cite journal |last1=Kharasch |first1=Morris S. |last2=Seyler |first2=Ralph C. |last3=Mayo |first3=Frank R. |title=Coördination Compounds of Palladous Chloride |journal=J. Am. Chem. Soc. |date=1938 |volume=60 |issue=4 |pages=882–884 |doi=10.1021/ja01271a035 |publisher=American Chemical Society}}</ref>

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 [[adduct]]s, such as [[bis(benzonitrile)palladium dichloride]] and [[bis(acetonitrile)palladium dichloride]].<ref>{{cite book | chapter = Bis(Benzonitrile)Dichloro Complexes of Palladium and Platinum | pages =60–63 | journal = [[Inorg. Synth.]] | volume = 28 | author = Gordon K. Anderson, Minren Lin | title =Inorganic Syntheses | doi = 10.1002/9780470132593.ch13 | date =2007 | isbn =9780470132593 }}</ref> These complexes are prepared by treating PdCl₂ with hot solutions of the nitriles:

:PdCl₂ + 2 RCN → PdCl₂(RCN)₂

Although occasionally recommended, [[air-free technique|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:<ref>{{OrgSynth | title = Palladium-catalyzed reaction of 1-alkenylboronates with vinylic halides: (1''Z'',3''E'')-1-Phenyl-1,3-octadiene | collvol = 8 | collvolpages = 532|author1-link=Norio Miyaura | author1 = Norio Miyaura|author2-link=Akira Suzuki (chemist)| author2= Akira Suzuki | year = 1993 | prep = cv8p0532}}</ref>

: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:<ref>{{cite book | journal = [[Inorg. Synth.]] | volume = 13 | pages = 121–124 | author = D. R. Coulson | doi = 10.1002/9780470132449.ch23 | year = 1972 | last2 = Satek | first2 = L. C. | last3 = Grim | first3 = S. O.| title = Inorganic Syntheses | chapter = Tetrakis(triphenylphosphine)palladium(0) | isbn = 9780470132449 }}</ref>

:PdCl₂(PPh₃)₂ + 2 PPh₃ + {{sfrac|5|2}} [[Hydrazine|N₂H₄]] → Pd(PPh₃)₄ + {{sfrac|1|2}} N₂ + 2 [[Hydrazinium chloride|{{chem|N|2|H|5|+|Cl|-}}]]

Alternatively, palladium(II) chloride may be solubilized in the form of the [[tetrachloropalladate|tetrachloropalladate(II)]] anion, such as in [[sodium tetrachloropalladate]], by reacting with the appropriate alkali metal chloride in water:<ref name = choueiry>{{cite book | title = Handbook of Organopalladium Chemistry for Organic Synthesis | editor = Ei-ichi Negishi | isbn = 0-471-31506-0 | year = 2002 | publisher = [[John Wiley & Sons, Inc.]] | chapter = II.2.3 Pd(0) and Pd(II) Complexes Containing Phosphorus and Other Group 15 Atom Ligands | author = Daniele Choueiry and Ei-ichi Negishi | chapter-url = https://books.google.com/books?id=mTMA2hExAaIC&pg=PA47 | chapter-format = [[Google Books]] excerpt}}</ref> Palladium(II) chloride is insoluble in water, whereas the product dissolves:

: PdCl₂ + 2 MCl → M₂PdCl₄

[[File:Tetrachloropalladate ions in aqueous solution.jpg|thumb|250px|left|A solution of [PdCl₄]²⁻(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.<ref>For example, http://www.marinecare.nl/assets/Uploads/Downloads/Leaflet-Passivation-Test-Kit.pdf{{dead link|date=March 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

: PdCl₂ + CO + H₂O → Pd + CO₂ + 2HCl

Residual PdCl₂ is converted to red [[palladium iodide|PdI₂]], the concentration of which may be determined colorimetrically:<ref>{{cite journal | author = T. H. Allen, W. S. Root | title = Colorimetric Determination of Carbon Monoxide in Air by an improved Palladium Chloride Method | url = http://www.jbc.org/content/216/1/309 | journal = [[J. Biol. Chem.]] | year = 1955 | volume = 216 | pages = 309–317 | pmid = 13252030 | issue = 1| doi = 10.1016/S0021-9258(19)52307-9 | doi-access = free }}</ref>

: PdCl₂ + 2 KI → PdI₂ + 2 KCl

Palladium(II) chloride is used in the [[Wacker process]] for production of [[aldehyde]]s and [[ketone]]s from [[alkene]]s.

Palladium(II) chloride can also be used for the cosmetic tattooing of [[Cornea#Function|leukomas]] in the [[cornea]].

{{Chlorides}}

[[Category:Platinum group halides]]