Overview Organopalladium

1 overview

1.1 palladium alkene complexes
1.2 palladium allyl complexes
1.3 palladium-carbon sigma-bonded complexes
1.4 palladium insertion compounds

overview

in contrast next-door neighbors group 11 elements, element palladium in organic chemistry not involve preparation of organopalladium compounds rather organopalladium reactive intermediates. on top of in many reactions catalytical amounts of metal used.

palladium alkene complexes

palladium reacts alkenes form pi complex can react multitude of nucleophiles akin oxymercuration reaction. c-pd bond removed reduction or elimination. in industrially important wacker process, ethylene converted acetaldehyde palladium chloride. fullerene ligands bind palladium in similar ways ethylene.

palladium allyl complexes

allyl compounds suitable leaving groups react palladium(ii) salts pi-allyl complexes having hapticity 3 such allylpalladium chloride dimer. these intermediates react nucleophiles example carbanions derived malonates or amines in allylic amination depicted below

allylpalladium intermediates feature in trost asymmetric allylic alkylation , carroll rearrangement , oxo variation in saegusa oxidation.

palladium-carbon sigma-bonded complexes

various organic groups can bound palladium , form stable sigma-bonded complexes. currently, alkyl, vinyl, aryl, , alkynyl complexes pd-c(sp3), pd-c(sp2), pd-c(sp) bonds equally well-known. stability of bonds in terms of bond dissociation energy follows trend: pd-alkynyl > pd-vinyl ≈ pd-aryl > pd-alkyl , metal-carbon bond length changes in opposite direction: pd-alkynyl < pd-vinyl ≈ pd-aryl < pd-alkyl.

palladium insertion compounds

zerovalent pd(0) compounds such tris(dibenzylideneacetone)dipalladium(0) , tetrakis(triphenylphosphine)palladium(0) react halocarbon r-x in oxidative addition r-pd-x intermediates covalent pd-c bonds. chemistry forms basis of large class of organic reactions called coupling reactions (see palladium-catalyzed coupling reactions). example sonogashira reaction:

palladium(ii) trifluoroacetate has been demonstrated effective in aromatic decarboxylation:

in proposed reaction mechanism pd(ii) replaces carboxylic acid proton while losing tfa group, carbon dioxide lost in first-order reaction , tfa destroys formed ar-pd-tfa complex without pd changing oxidation state.