Organopalladium(iv) chemistry

Abstract

Although the chemistry of Pd(0), Pd(I) and Pd(II) is well established, high oxidation state Pd(IV) complexes are less well-known. This situation has highly changed in recent years. Many well-defined Pd(IV) complexes has been isolated and characterized, providing evidence for a series of proposed Pd(II)/Pd(IV) catalytic reactions. A deep understanding of the behavior of Pd(IV) complexes could lead to the design and development of novel reactions that could not be accessed by traditional Pd(0)/Pd(II) chemistry. This critical review describes the stoichiometric reactions of Pd(IV) complexes and discusses their potential mechanism in catalytic reactions (137 references).

Redox-Induced Aromatic C–H Bond Functionalization in Metal Complex Catalysis from the Electrochemical Point of View

“…The first reduction peak potential of PhI(OAc) 2 was found to occur equally both in the CH 3 CN solution and in the carbon paste electrode (1.70 V vs. Fc + /Fc) as a two-electron process. These redox properties are in good agreement with the experimental data on their high oxidative ability, as hypervalent iodine oxidants have been used for the two-electron oxidations of numerous Pd(II) to Pd(IV) cyclometallated complexes [3,7,8,[10][11][12][26][27][28][29]31].…”

“…The chemistry of palladium (Pd) compounds in higher oxidation states is extremely useful in oxidative functionalizations, in which a C-H bond can be catalytically converted into another functional group [1,[6][7][8][9][10][11][12]. One of the major problems in Pd(II)/Pd(III)/Pd(IV) chemistry, however, is that the co-oxidants used are either expensive to purchase (silver and other metal salts are often used), or to separate from the product mixture (particularly in the case of high molecular weight organic oxidants).…”

NCN–Pincer–Pd Complex as Catalyst for the Hiyama Reaction in Biomass-Derived Solvents

“…13 Since, in general, better results were obtained in neat glycerol than in the corresponding eutectic mixture with ChCl, two control experiments were performed trying to decide if Clanions could be occupying a vacant in the coordination sphere of the complex and thus, limiting its catalytic activity. The model reaction was carried out employing catalyst 4', bearing an Clanion instead of an I -(see ESI for details).…”

“…12 Reactions such as the Suzuki, Heck or Sonogashira couplings often take place under classical Pd (0)/Pd (II) catalytic cycle, 3 although there are some reports regarding the use of Pd (II)/Pd (IV) species. 13 These cross-coupling reactions permit the synthesis of relatively complex molecules, forming carbon-carbon or carbon-heteroatom bonds in a simple way. This approach has been applied in several processes, both in industry and academia.…”

Rhodium(I)‐Catalyzed Redox‐Economic Cross‐Coupling of Carboxylic Acids with Arenes Directed by N‐Containing Groups

“…[1] For more efficient and greener methods to construct CÀC bonds, much attention has been paid to direct CÀH functionalization, starting from arenes (Scheme 1 A), in the past several decades. [2] Among these modern couplings, the coupling partners can be organic halides/pseudohalides, [3] organometallic reagents, [4] and even another arene. [5] Carboxylic acids are considered another important carbon source because of its ready availability, stability, and nontoxicity.…”