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Pd(PPh 3) 4 is widely used as a catalyst for palladium-catalyzed coupling reactions. [7] Prominent applications include the Heck reaction, Suzuki coupling, Stille coupling, Sonogashira coupling, and Negishi coupling. These processes begin with two successive ligand dissociations followed by the oxidative addition of an aryl halide to the Pd(0 ...
The Suzuki reaction or Suzuki coupling is an organic reaction that uses a palladium complex catalyst to cross-couple a boronic acid to an organohalide. [1] [2] [3] It was first published in 1979 by Akira Suzuki, and he shared the 2010 Nobel Prize in Chemistry with Richard F. Heck and Ei-ichi Negishi for their contribution to the discovery and development of noble metal catalysis in organic ...
One of the first applications of phosphine ligands in catalysis was the use of triphenylphosphine in "Reppe" chemistry (1948), which included reactions of alkynes, carbon monoxide, and alcohols. [16] In his studies, Reppe discovered that this reaction more efficiently produced acrylic esters using NiBr 2 (PPh 3) 2 as a catalyst instead of NiBr 2.
Palladium forms a variety of ionic, coordination, and organopalladium compounds, typically with oxidation state Pd 0 or Pd 2+. Palladium(III) compounds have also been reported. Palladium compounds are frequently used as catalysts in cross-coupling reactions such as the Sonogashira coupling and Suzuki reaction.
In the Appel reaction, a mixture of PPh 3 and CX 4 (X = Cl, Br) is used to convert alcohols to alkyl halides. Triphenylphosphine oxide (OPPh 3) is a byproduct. PPh 3 + CBr 4 + RCH 2 OH → OPPh 3 + RCH 2 Br + HCBr 3. This reaction commences with nucleophilic attack of PPh 3 on CBr 4, an extension of the quaternization reaction listed above.
The reaction occurs in two distinct steps. In the first step, PtCl 2 (PPh 3) 2 is generated. In the second step, this platinum(II) complex is reduced. The overall synthesis can be summarized as: K 2 [PtCl 4] + 2KOH + 4PPh 3 + C 2 H 5 OH → Pt(PPh 3) 4 + 4KCl + CH 3 CHO + 2H 2 O. Pt(PPh 3) 4 reacts with oxidants to give platinum(II) derivatives:
[9] [10] [1] Triphenylphosphine serves as both a ligand and a two-electron reducing agent that oxidizes itself from oxidation state (III) to (V). In the synthesis, three equivalents of triphenylphosphine become ligands in the product, while the fourth reduces rhodium(III) to rhodium(I). RhCl 3 (H 2 O) 3 + 4 PPh 3 → RhCl(PPh 3) 3 + OPPh 3 + 2 ...
These complexes react with halocarbon R-X in oxidative addition to R-Pd-X intermediates with covalent Pd-C bonds. This chemistry forms the basis of a large class of organic reactions called coupling reactions (see palladium-catalyzed coupling reactions). An example is the Sonogashira reaction: