Stereochemistry of Nucleophilic Attack on Olefins coordinated to Platinum(II) and Palladium(II)

Abstract

THERE is an interesting difference between the stereochemistry of nucleophilic attack on chelating diolefins and mono-olefins coordinated to platinum(II) or palladium(II), because the former give trans-addition of nucleophiles across the double bond (reaction (1))1–4, whereas the kinetic results for the oxidative hydrolysis of mono-olefins coordinated to palladium(II) are only consistent with cis-addition5,6. Although at 25° C di-olefin complexes of palladium(II) give trans-addition of methoxide ion to the double-bond and no reduction to the metal7, at higher temperatures reduction to palladium metal is observed8 and vinyl ethers—the normal oxidative-addition products9—are isolated7. Thus for di-olefin complexes, trans-addition is favoured at low temperatures, but for mono-olefin complexes cis-addition is favoured. In the oxidative acetylation of mono-olefins coordinated to palladium(II) both cis and trans-addition mechanisms occur simultaneously10.