The triple condensation of cyclopentanone or indanone to trindane (C15H18) or truxene (C27H18), respectively, provides convenient access to molecular skeletons on which major fragments of the prototypical fullerene C60 can be assembled. In particular, early approaches (both organic and organometallic) towards sumanene, as well as the final successful synthesis, are described. Organometallic derivatives of trindane have been prepared in which Cr(CO)3, Mo(CO)3, [Mn(CO)3]+ or [(C5H5)Fe(CO)2]+ are η6-bonded to the central arene ring. The debromination of hexabromotrindane yields trindene, which forms a tri-anion to which as many as three organometallic fragments, such as Mn(CO)3, W(CO)3Me, or Rh(CO)2, may be attached. Truxene forms complexes whereby three metal fragments can bind either to the peripheral arene rings, or to the five-membered rings, and these can be interconverted via η6 ↔ η5 haptotropic shifts. Truxene also forms a double-decker sandwich with Ag(I) bridges, and decacyclene, C36H18, forms triple-decker sandwiches bearing multiple cyclopentadienyl-nickel or -iron moieties. The organic chemistry of trindane has been investigated, especially with respect to its unexpectedly complex oxidation products, which were only identified unambiguously via X-ray crystallography. The three-fold symmetric trindane framework has also been used as a template upon which a potential artificial receptor has been constructed. Finally, the use of truxene and truxenone derivatives in a wide range of applications is highlighted.
Keywords: C60 fragments; X-ray crystallography; ketone triple condensations; metal π-complexes; polycyclic frameworks; three-fold symmetry.