Gas-phase studies of alkene oxidation by transition-metal oxides. Ion-beam studies of CrO⁺

Abstract

An examination of reaction thermochemistry and metal oxide bond dissociation energies focuses attention on the chromium oxide ion as an interesting candidate for investigations of hydrocarbon oxidation processes. Reactions of this species, formed by surface ionization, have been examined with ion-beam reactive scattering techniques. In reactions with alkenes, CrO⁺ abstracts allylic hydrogen to form CrOH⁺ and adds to double bonds to yield aldehydes and other products which are rationalized by postulating metallacyclic intermediates. In comparison with other first-row transition-metal oxides, which are either too stable (Sc, Ti, and V) or too reactive (Mn, Fe, Co, and Ni), CrOAn examination of reaction thermochemistry and metal oxide bond dissociation energies focuses attention on the chromium oxide ion as an interesting candidate for investigations of hydrocarbon oxidation processes. Reactions of this species, formed by surface ionization, have been examined with ion-beam reactive scattering techniques. In reactions with alkenes, CrO⁺ abstracts allylic hydrogen to form CrOH⁺ and adds to double bonds to yield aldehydes and other products which are rationalized by postulating metallacyclic intermediates. In comparison with other first-row transition-metal oxides, which are either too stable (Sc, Ti, and V) or too reactive (Mn, Fe, Co, and Ni), CrO⁺ exhibits a balance in being reactive but selective. Bond dissociation energies derived in this study include Z) An examination of reaction thermochemistry and metal oxide bond dissociation energies focuses attention on the chromium oxide ion as an interesting candidate for investigations of hydrocarbon oxidation processes. Reactions of this species, formed by surface ionization, have been examined with ion-beam reactive scattering techniques. In reactions with alkenes, CrO⁺ abstracts allylic hydrogen to form CrOH⁺ and adds to double bonds to yield aldehydes and other products which are rationalized by postulating metallacyclic intermediates. In comparison with other first-row transition-metal oxides, which are either too stable (Sc, Ti, and V) or too reactive (Mn, Fe, Co, and Ni), CrO⁺ exhibits a balance in being reactive but selective. Bond dissociation energies derived in this study include D°(Cr⁺-O) = 85.3 ± 1.3 kcal mol⁻¹ and D°(Cr-O) = 110 ± 2 kcal mol⁻¹.