Structural analysis of products from the C-60-piperazine reaction. Consistent geometric distortions of the fullerene core upon adduct formation.

The reaction of C-60 with piperazine yields the single addition product, C60N2(C2H4)(2), and six double addition products which can be chromatographically separated. Of these, single crystal X-ray diffraction characterization has produced structural data for the identification of (C2H4)(2)N2C60 and three isomeric forms of the double addition product, {(C2H4)(2)N-2}C-2(60) Addition of the N-2(C2H4)(2) units produces local distortions of the fullerene core which involve marked elongation of the C-C bond at the 6:6 ring junction that is involved in the addition and outward displacement of these carbons from their usual positions by ca 0.33-0.40 Angstrom. The combined effects of double addition can produce local distortions that appear visually more severe but which retain the structural features found in the single addition product. (C) 1996 Elsevier Science Ltd