Controlled and Chemoselective Hydrogenation of Nitrobenzene over Ru@C₆₀ Catalysts

Abstract

Electron-deficient ruthenium nanoparticles supported on Ru fulleride nanospheres allow the successive and chemoselective hydrogenation of nitrobenzene to aniline and then to cyclohexylamine. The catalysts were prepared in a straightforward manner by decomposition under dihydrogen of [Ru(COD)(COT)] in the presence of C60. The nitrobenzene hydrogenation reaction is solvent sensitive and proceeds more quickly in methanol than in other alcohols. The same behavior, i.e. a two-step successive hydrogenation, has been observed for several substituted nitroarenes. Density functional theory calculations suggest that the observed chemoselectivity is mainly governed by the presence of surface hydrides on the electron-deficient Ru nanoparticles. At the threshold value of 1.5 H per Ru surface atom, the formation of aniline is favored due to the net preference of the NO2 coordination.