Oxidative Reactions with Pd II Compounds

In addition to CuCfi, some other compounds such as Cu(OAc)2, Cu(N03)2-FeCl.i, dichromate, HNO3, potassium peroxodisulfate, and Mn02 are used as oxidants of Pd(0). Also heteropoly acid salts comtaining P, Mo, V, Si, and Ge are used with PdS04 as the redox system[2]. Organic oxidants such as benzo-quinone (BQ), hydrogen peroxide and some organic peroxides are used for oxidation. Alkyl nitrites are unique oxidants which are used in some industrial 

In the Wacker process, the reaction is actually carried out in dilute HCl at a high concentration of chloride ion and an elevated temperature. The high concentration of CUCI2 shifts the equilibrium further to the right. 

Palladium Reagents and Catalysts—New Perspectives for the 21st Century J. Tsuji 2004 John Wiley Sons, Ltd ISBNs 0-470-85032-9 (HB) 0-470-85033-7 (PB) 

An important Pd(II)-generation step in Pd(II)-catalyzed reactions is the elimination of heteroatom groups such as Cl, Br, OAc and OH at )3-position to Pd, and Pd(JI) species are generated after the elimination. Elimination of heteroatom groups is faster than that of hydrogen. No reoxidant is required for this efficient catalytic reaction. Based on this reaction, 1,2-dichloro- and dibromoethane derivatives [10], a-halo ketones such as chloroacetone and desyl chloride are used for Pd(II) generation [11,12]. 

Another important Pd(II)-generation step is protonolysis with acids. For example, alkenylpalladium intermediates formed by palladation of alkynes with 

Pd(II) are living species, because there is no possibility of y3-H elimination. So Pd(II)X2 is generated from these Pd intermediates by protonolysis with HX, or oxidative halogenation with C11X2. In such a case, the reaction proceeds with a catalytic amount of Pd(II) salt without reoxidants. 

One important method for the oxidation reaction using Pd(II) is a gas phase reaction using a solid Pd catalyst supported on active carbon or alumina. Actually vinyl acetate and allyl acetate are produced commercially in a gas phase by using the supported Pd catalyst. It is assumed that Pd(0) is oxidized efficiently to Pd(II) with oxygen on the surface of the support. 

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Stoichiometric Oxidative Reactions with Pd(II) Compounds in which Pd(II) is Reduced to Pd(0)... 

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