The +IV Oxidation State in Organopalladium Chemistry RECENT ADVANCES AND POTENTIAL INTERMEDIATES IN ORGANIC SYNTHESIS AND CATALYSIS

The organometallic chemistry of palladium is dominated by the + I I oxida-tion state, and the chemistry of complexes containing simple organic groups bonded to palladium in the + I V oxidation state has developed only recently Organic synthesis and catalytic reactions that may involve undetected palla-dium ( I V) intermediates have been suggested frequentlx and the new oxidation state + I V chemistry provides some support for these proposals, and gives encouragement for the development of new systems involving palladium ( I V) . The chemistry of organopalladium ( I V) is reviewed here, and possible cat-alytic roles forpalladium ( I V) are discussed. The synthesis and decomposition reactions of palladium ( I V) complexes provide "models " for catalytic pro-posals. The palladium ( I V) complexes are formed by oxidative addition of organohalides to palladium ( I I) complexes, and most complexes decompose under mild conditions by carbon-carbon bond formation in reductive elimina-tion reactions, for example, for methyl(pheny1) (2,2'-bipyridyl)palladium ( I I) as a substrate, oxidative addition of benzyl bromide give