Allylpalladium(II) chloride dimer

Names
IUPAC name Allylpalladium(II) chloride dimer
Other names Allylpalladium chloride dimer bis(allyl)di-μ-chloro-dipalladium(II) APC
Identifiers
CAS Number	12012-95-2 Y
3D model (JSmol)	Interactive image
ChemSpider	21171401 Y
ECHA InfoCard	100.031.423
EC Number	234-579-8
PubChem CID	61538
CompTox Dashboard (EPA)	DTXSID10897423
InChI InChI=1S/2C3H5.2ClH.2Pd/c2*1-3-2;;;;/h2*3H,1-2H2;2*1H;;/q;;;;2*+1/p-2 Y Key: TWKVUTXHANJYGH-UHFFFAOYSA-L Y InChI=1/2C3H5.2ClH.2Pd/c2*1-3-2;;;;/h2*3H,1-2H2;2*1H;;/q;;;;2*+1/p-2/r2C3H5ClPd/c2*1-2-3-5-4/h2*2H,1,3H2 Key: TWKVUTXHANJYGH-NNVIZEFPAF
SMILES Cl[Pd]CC=C.C=CC[Pd]Cl
Properties
Chemical formula	C6H10Cl2Pd2
Molar mass	365.85 g/mol
Appearance	Pale yellow, crystalline solid
Melting point	decomp at 155-156 °C
Solubility in water	Insoluble
Solubility in other solvents	Chloroform benzene acetone methanol
Structure[1]
Crystal structure	monoclinic
Space group	P21/n, No. 14
Formula units (Z)	2
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H312, H315, H319, H332, H335
Precautionary statements	P261, P264, P270, P271, P280, P301+P312, P302+P352, P304+P312, P304+P340, P305+P351+P338, P312, P321, P322, P330, P332+P313, P337+P313, P362, P363, P403+P233, P405, P501
Safety data sheet (SDS)	http://www.colonialmetals.com/pdf/5048.pdf
Related compounds
Related compounds	(η3-allyl)(η5 – cyclopentadienyl)palladium(II) di-μ-chlorobis(crotyl)dipalladium
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Allylpalladium(II) chloride dimer (APC) is a chemical compound with the formula [(η³-C₃H₅)PdCl]₂. This yellow air-stable compound is an important catalyst used in organic synthesis.^[2] It is one of the most widely used transition metal allyl complexes.

The compound has a dimeric structure that is centrosymmetric. Each allyl group lies in a plane at an angle of about 111.5° to the square formed by the palladium and carbon atoms, and the Pd–C distances are all equal. Its unit cell is monoclinic.^[1]

The compound is prepared by purging carbon monoxide through a methanolic aqueous solution of sodium tetrachloropalladate (prepared from palladium(II) chloride and sodium chloride), and allyl chloride.^[2]

2 Na₂PdCl₄   +   2 CH₂=CHCH₂Cl   +   2 CO   +   2 H₂O   →   [(η³-C₃H₅)PdCl]₂   +   4 NaCl   +   2 CO₂   +   4 HCl

Another method is the reaction of propene with palladium(II) trifluoroacetate, followed by ion exchange with chloride:^[3]

2 (CF₃COO)₂Pd + 2 CH₂=CHCH₃ → [(η³-C₃H₅)Pd(CF₃COO)]₂

[(η³-C₃H₅)Pd(CF₃COO)]₂ + 2 Cl⁻ → [(η³-C₃H₅)PdCl]₂ + 2 CF₃COO⁻

APC reacts with sources of cyclopentadienyl anion to give the corresponding 18e⁻ complex cyclopentadienyl allyl palladium:

[(η³-C₃H₅)PdCl]₂   +   2 NaC₅H₅   →   2 [(η⁵-C₅H₅)Pd(η³-C₃H₅)]   +   2 NaCl

The dimer reacts with a variety of Lewis bases (:B) to form adducts (η³-C₃H₅)PdCl:B. Its reaction with pyridine and the corresponding enthalpy are:

1/2 [(η³-C₃H₅)PdCl]₂ + :NC₅H₅ → (η³-C₃H₅)PdCl:NC₅H₅ ΔH=−30.1 kJ.mol⁻¹

This enthalpy corresponds to the enthalpy change for a reaction forming one mole of the product, (η³-C₃H₅)PdCl:NC₅H₅, from the acid dimer. The dissociation energy for the Pd dimer, which is an energy contribution prior to reaction with the donor,

[(η³-C₃H₅)PdCl]₂ → 2 (η³-C₃H₅)PdCl

has been determined by the ECW model to be 28 kJ.mol⁻¹.

APC catalyzes many organic reactions, such as cross-coupling, nucleophilic addition to dienes, and decomposition of diazo compounds to reactive carbenes. It is also a useful precursor of other Pd catalysts.^[3]