ELECTRON-SPIN-RESONANCE INVESTIGATIONS OF RUTHENIUM SUPPORTED ON GAMMA-ALUMINA

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.