Syntheses and crystal structures of azafulleroid and aziridinofullerene bearing silyl or germyl benzene

Addition of silyl and germylmethyl azides (1) to fullerene C60 at 50 °C through [2+3] cycloaddition led to the formation of the triazoline adducts (2). Subsequently, heating 2 at 100 °C in the solid state, caused N2 extrusion producing two different isomers, [5,6]-azafulleroid (3) and [6,6]-aziridinofullerene (4). The 13C NMR spectrum of 3 had an absence of resonances in the aliphatic region for the fullerene C60 cage, showing a fulleroid with CS symmetry. In contrast, 4 exhibited one sp3 resonance in the aliphatic region for the fullerene C60 cage, indicative of an aziridinofullerene with C2V symmetry. However, MALDI-TOF mass characterization was hampered because ion peaks corresponding to the bis-adduct are detected in positive ion mode measurements, whereas the ion peaks [M−N2]− for 2a as well as [M]− for 3a and 4a are observed in negative ion measurements. In an effort to obtain X-ray data, silyl and germylphenyl groups were introduced to form intermolecular complexes with fullerene C60. The X-ray structures of 3c and 3d revealed a strong enhancement of homoconjugation in the bridged annulene moiety based on POAV analysis. The X-ray structures of 3c,d and 4c were confirmed with the detection of silyl and germylphenyl-C60 interactions, similar to dimethoxyphenyl-C60 interactions.