Role of <i>d</i>-Orbitals in the Catalytic Activation of Molecular Oxygen in the Liquid-Phase Oxidation

Abstract

The catalytic activation of molecular oxygen by various onium compounds were interpreted theoretically with particular attention to the role of d-orbitals. We made several findings. First, there exists a parallelism between the catalytic activities of onium compounds and the AO population on the nonbonding p-orbital or the partially occupied d-orbitals of their central atoms. Second, the preferred mode of the interaction between onium compounds and molecular oxygen was expressed by the parallel form (see Fig. 2). Third, the above interaction was confirmed by the red shift of the band near 200mμ of the transition, nonbonding 2p AO→3d AO on the central sulfur of sulfonium compounds, in an oxygen atmosphere. Finally, the process of the hydrogen abstraction of molecular oxygen activated by onium compounds from a hydrocarbon was discussed.