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Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C 6 H 5) 3 and often abbreviated to P Ph 3 or Ph 3 P. It is versatile compound that is widely used as a reagent in organic synthesis and as a ligand for transition metal complexes, including ones that serve as catalysts in organometallic chemistry.
For stabilized Wittig reagents bearing conjugated electron-withdrawing groups, even relatively weak bases like aqueous sodium hydroxide or potassium carbonate can be employed. [Ph 3 PCH 3] + Br −, typical phosphonium salt. The identification of a suitable base is often an important step when optimizing a Wittig reaction.
A metal-phosphine complex is a coordination complex containing one or more phosphine ligands. Almost always, the phosphine is an organophosphine of the type R 3 P (R = alkyl, aryl).
An electron-withdrawing group (EWG) is a group or atom that has the ability to draw electron density toward itself and away from other adjacent atoms. [1] This electron density transfer is often achieved by resonance or inductive effects.
Reactions between sp 3-sp 3 centers are often more difficult; however, adding an unsaturated ligand with an electron withdrawing group as a cocatalyst improved the yield in some systems. It is believed that added coordination from the unsaturated ligand favors reductive elimination over β-hydride elimination.
Reductive elimination is sensitive to a variety of factors including: (1) metal identity and electron density, (2) sterics, (3) participating ligands, (4) coordination number, (5) geometry, and (6) photolysis/oxidation. Additionally, because reductive elimination and oxidative addition are reverse reactions, any sterics or electronics that ...
The electron-withdrawing group (EWG) alpha to the phosphonate is necessary for the final elimination to occur. In the absence of an electron-withdrawing group, the final product is the β-hydroxyphosphonate 3a and 3b. [14] However, these β-hydroxyphosphonates can be transformed to alkenes by reaction with diisopropylcarbodiimide. [15]
Wilkinson's catalyst is usually obtained by treating rhodium(III) chloride hydrate with an excess of triphenylphosphine in refluxing ethanol. [9] [10] [1] Triphenylphosphine serves as both a ligand and a two-electron reducing agent that oxidizes itself from oxidation state (III) to (V).