Synthesis and Structure of an Open-Cage Thiafullerene C₆₉S: Reactivity Differences of an Open-Cage C₇₀ Tetraketone Relative to Its C₆₀ Analogue

An open-cage C₇₀ fullerene with a 13-membered ring-opening and a bis­(hemiacetal) moiety was synthesized by the reaction of the corresponding open-cage C₇₀ diketone with nucleophilic oxidizing agents. The size of the cage opening could be expanded by a subsequent dehydration reaction. Reaction of the thus obtained open-cage C₇₀ tetraketone with elemental sulfur in the presence of tetrakis­(dimethylamino)­ethylene resulted in the formation of the first example of an open-cage C₆₉S thiafullerene with a 12-membered ring-opening. The formation of this sulfur-containing heterofullerene reflects a significantly different chemical reactivity for the open-cage C₇₀ tetraketone relative to its C₆₀ analogue. The structures of all novel compounds were unambiguously determined by single crystal X-ray diffraction analyses, in addition to which the electrochemical properties of the thiafullerene C₆₉S were examined and compared with those of the corresponding C₇₀ analogue.