Interaction of carbon monoxide with Ru/γ-Al2O3. An electron spin resonance investigation

Abstract

Interaction of carbon monoxide with Ru/γ-Al₂O₃ leads to the formation of Ru^I and Ru^III carbonyl derivatives. The relative amounts of the two species are a function of the temperature used in decarbonylating the Ru₃(CO)₁₂/γ-Al₂O₃ precursor. The thermal and vacuum stabilities of the Ru^I derivative [g_⊥= 2.050, g_‖= 1.992, A_‖(⁹⁹Ru, ¹⁰¹Ru)= 28 G] and the Ru^III derivative (g_‖= 2.046, g_⊥= 2.005) are different, the Ru^III species being the more stable. The Ru—CO bond strength of these carbonyls is high in comparison with that of the analogous Rh/γ-Al₂O₃ carbonyl derivatives. The enhanced bond strength may account for the difference in the catalytic behaviour between the Ru and Rh systems.