Chemical Properties
Brown needles, soluble in benzene and toluene, insoluble in ether and alcohol, keep in dark and refrigerated.
Uses
Palladium (II) Acetate Trimer is used in Suzuki-Miyaura cross-coupling reactions and a catalyst for intramolecular coupling. It also serves to catalyze the chemoselective reduction of nitroarenes.
Definition
Palladium acetate is a chemical compound of palladium. It is used as a catalyst for many organic reactions and as a precursor to other palladium(II) compounds. Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is found as a free metal alloyed with gold and other platinum group metals and in the rare minerals cooperite and polarite. (Toxin and Toxin Target Database (T3DB))
Preparation
The synthesis of palladium acetate was first reported by Wilkinson et al.,where glacial acetic acid containing palladium powder is heated at reflux with a minimal amount of nitric acid until the generation of brown NOx fumes ceases. Although this is a relatively old method, it is still the most commercially employed route for the synthesis of palladium acetate, considering the process economics. Palladium (II) Acetate can be synthesized in two steps from palladium sponge via the intermediate dinitrate by first combining it with hot glacial acetic acid and nitric acid:
Pd + 2 HNO3 → Pd(NO3)2 + H2
Pd(NO3)2 + 2 CH3COOH → Pd(O2CCH3)2 + 2 HNO3
Reactions
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Efficient catalyst for the arylation of olefins (Heck reaction).
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Catalyst for cross-coupling reactions.
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Catalyst for C-H activation.
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Precatalyst for enantioselective decarboxylative protonation of allyl β-ketoesters.
General Description
Palladium(II) acetate is a homogenous oxidation catalyst. It participates in the activation of alkenic and aromatic compounds towards oxidative inter- and intramolecular nucleophilic reactions. Crystals of palladium(II) acetate have a trimeric structure, having symmetry
D3h. Each of the palladium atoms in the crystals are joined to the other two by double acetate bridges. Microencapsulation of palladium(II) acetate in polyurea affords polyurea-encapsulated palladium(II) acetate. It is a versatile heterogeneous catalyst for various phosphine-free cross-coupling reactions. It participates as catalyst in the Heck coupling reaction of pthalides with different alkenes.
Flammability and Explosibility
Non flammable
reaction suitability
reagent type: oxidant
Safety Profile
Moderately toxic by ingestion. When heated to decomposition it emits toxic vapors of palladium.
Synthesis
The general procedure for the synthesis of palladium acetate from palladium carbon and glacial acetic acid is as follows: Recovered palladium powder (10.3 g, 0.9 eq.) is added to a mixture of glacial acetic acid (200 ml) and nitric acid (0.5 ml), followed by refluxing the reaction for 30 minutes. After completion of the reaction, the brown solution was obtained by filtration while hot. The filtrate was concentrated until about 20 ml of glacial acetic acid remained and stopped. Palladium acetate crystals gradually precipitated at the bottom of the beaker at room temperature. The recovered palladium acetate (20 g, 92% yield) was finally obtained by diafiltration operation.
Purification Methods
It recrystallises from CHCl3 as purple crystals. It can be washed with AcOH and H2O and dried in air. Large crystals are obtained by dissolving it in *C6H6, adding half its volume of AcOH and allowing it to evaporate slowly at room temperature. It forms green adducts with nitrogen donors, it dissolves in KI solution to form solid PdI2 and a red solution of PdI42-, but is insoluble in aqueous saturated NaCl, and NaOAc. It dissolves in HCl to form PdCl42-. It is soluble in CHCl3, CH2Cl2, Me2CO, MeCN, Et2O, but it is insoluble in H2O, and decomposes when warmed in alcohols in which it is also insoluble. [Morehouse et al. Chem Ind (London) 544 1964, Stephenson et al. J Chem Soc 3632 1965, Skapski & Smart J Chem Soc (D) 658 1970, Heck Acc Chem Res 12 146 1979.]
References
[1] Inorganica Chimica Acta, 1999, vol. 294, # 1, p. 99 - 102
[2] Journal of Asian Natural Products Research, 2017, vol. 19, # 6, p. 623 - 629
[3] Russian Journal of General Chemistry, 2006, vol. 76, # 5, p. 747 - 752
[4] Russian Chemical Bulletin, 2003, vol. 52, # 6, p. 1376 - 1379
[5] Acta Crystallographica Section C: Crystal Structure Communications, 2004, vol. 60, # 9, p. m449-m450
