Electron Microscopic Imaging of a Single Group 8 Metal Atom Catalyzing C–C Bond Reorganization of Fullerenes
mediaposted on 14.09.2011 by Eiichi Nakamura, Masanori Koshino, Takeshi Saito, Yoshiko Niimi, Kazu Suenaga, Yutaka Matsuo
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Heating a bulk sample of fullerene complexes, (η5-C5H5)MC60R5 (M = Fe, Ru, R = Me, Ph), produces small hydrocarbons because of coupling of R and C5H5 via C–C and C–H bond activation. Upon observation by transmission electron microscopy, these complexes, encapsulated in single-walled carbon nanotubes, underwent C–C bond reorganization reactions to form new C–C bond networks, including a structure reminiscent of fullerene. Quantitative comparison of the electron dose required to effect the C–C bond reorganization of fullerenes and organofullerenes in the presence of a single atom of Ru, Fe, or Ln and in the the absence of metal atoms indicated high catalytic activity of Ru and Fe atoms, as opposed to no catalytic activity of Ln. Organic molecules such as hydrocarbons and amides as well as pristine fullerene maintain their structural integrity upon irradiation by ca. 100 times higher electron dose compared to the Ru and Fe organometallics. The results not only represent a rare example of direct observation of a single-metal catalysis but also have implications for the use of single metal atom catalysis in Group 8 metal heterogeneous catalysis.