SELECTIVE TUNING OF THE AFFINITY OF PALLADIUM-CENTERED COMPLEXES FOR DIOXYGEN BY 2-ELECTRON TRANSFER STEPS - APPLICATION TO THE CHEMICAL-SEPARATION OF DIOXYGEN FROM GASEOUS-MIXTURES

Dioxygen is fixed quantitatively by zerovalent low-ligated palladium-c entered complexes which are electrogenerated by two-electron reduction of their dichloropalladium(II) parent complexes. The resulting peroxo palladium complexes are oxidizable. In the presence of chloride ions, this oxidation involves a two-electron process that regenerates the d ichloropalladium(II) parent complexes and dioxygen. Based on such two- electron transfer, facile tuning of the affinity of palladium-centered complexes for dioxygen allows us to propose a chemical method for the separation of dioxygen from gaseous mixtures. Two situations are enco untered, which depend on the reduction potentials of dioxygen and the dichloropalladium(II) parent complexes. When dioxygen is less easily r educed than the dichloropalladium(II) complex, fixation of dioxygen oc curs by its oxidative addition to a chloride-ligated zerovalent pallad ium-centered species. When dioxygen is more easily reduced than the di chloropalladium(II) complex, fixation proceeds through reaction of sup eroxide ion with the dichloropalladium(II) complex.