Electron spin resonance investigations of ruthenium supported on γ-alumina

Abstract

We report an electron spin resonance investigation performed on alumina-supported ruthenium, Ru/γ-Al₂O₃, obtained by decarbonylation (pyrolysis or H₂ reduction) of Ru₃(CO)₁₂/γ-Al₂O₃. The spectra observed after Ru/γ-Al₂O₃ was in contact with O₂, CO, NO ‘probe’ molecules allow one to distinguish superoxide, carbonyl and nitrosyl paramagnetic derivatives of ruthenium, and show that ruthenium centers in formal oxidation states other than the zero metal state become stable by interaction with γ-Al₂O₃. The strength of the interaction between paramagnetic ruthenium centres and π^*-acceptor molecules (O₂, CO and NO) is dependent both on the π^*-acceptor molecules and on the decarbonylation method.