Unusual polymerization in the Li4C60 fulleride
  Li4C60, one of the best representatives of lithium intercalated fullerides, features a novel type of 2D polymerization. Extensive investigations, including laboratory x-ray and synchrotron radiation diffraction, 13C NMR, MAS and Raman spectroscopy, show a monoclinic I2/m structure, characterized by chains of [2+2]-cycloaddicted fullerenes, sideways connected by single C-C bonds. This leads to the formation of polymeric layers, whose insulating nature, deduced from the NMR and Raman spectra, denotes the complete localization of the electrons involved in the covalent bonds. 
M. Ricco, T. Shiroka, M. Belli, D. Pontiroli, M. Pagliari, G. Ruani,   D. Palles, S. Margadonna, M. Tomaselli