Diverse families of cyclophanes [1] and assorted cage compounds [2] with novel structures and properties continue to be topics of wide-spread interest. [3] Earlier, we reported the synthesis of a novel class of enediyne cyclophanes by sequential palladium-or copper-mediated coupling. [4] In contrast to normal [n.m]paracyclophanes, the rotation of the benzene ring in these molecules is not restricted by the bridging bonds. Consequently they were christened revolveneynes 1 as the aromatic rings rotate freely, with ªskipping ropeº-type properties, in which the bridging units and one aromatic ring may swing around each other. The unsaturated bonds in these bridges impart a helical twist to the structures. As a result, they possess helical chirality, a property that is shared with related D 2 -symmetric olefinic paracyclophanes. [5] In a related area, we [6] and others [7] have attemped to extend these syntheses to multibridged systems in order to prepare potential precursors to fullerenes such as C 60 , but with limited success. However, Vollhardt and co-workers [8] have demonstrated that 2 decomposed explosively to form carbon onions when heated, and cobalt alkyne complexes afforded carbon nanotubes.
substituents on the indium atoms. The synthesis and structure of 1 also suggest that the extrusion of part of the ligand array in simple clusters such as R 2 MMR 2 (M Ga, In) or (InR) n to give higher clusters that incorporate unsubstituted metal atoms may be a general phenomenon in these sterically crowded species. Another distinctive feature of the synthesis of 1 is that an In I compound was employed as starting material. This already has a 1:1 metal:ligand ratio and is closer stoichiometrically to the more highly aggregated cluster product 1 than are the higher valent starting materials, which usually carry two substituents per metal atom. It now seems likely that further examples of these interesting species will be isolated not only for indium but also for the other Group 13 metals.
Experimental Section
Under anaerobic and anhydrous conditions, a pale yellow solution of LiC 6 H 3 -2,6-Mes 2 (1.60 g, 4.99 mmol) in THF (20 mL) was cooled to ca. À 78 8C and added dropwise to a yellow suspension of InCl (0.82 g, 5.5 mmol) in THF (5 mL) at ca. À 78 8C. The solution became dark orangebrown upon addition and was stirred for 30 min. The solution was warmed to À 15 8C, and the THF was removed under reduced pressure. The orangebrown solid was extracted with hexanes (100 mL) and gravity filtered through a Celite pad. The volume of the orange-brown solution was reduced to 30 mL. Cooling to ca. 0 8C for 12 h produced dark brown crystals