Amphiphilic C(60) derivatives of [(ethoxycarbonyl)decylene]fullerene and bis[(ethoxycarbonyl)decylene]fullerene, which are used to obtain organized molecular films by the LB technique, were prepared by the reaction of C(60) with diazo compounds. They were characterized by IR, UV-vis, (1)H-NMR, (13)C-NMR, and FD-MS. Direct evidence confirmed that the [6,5]-fullerenoid is the thermodynamically more stable isomer. It was converted from the arrangement of a [6,6]methanofullerene rather than a reaction product in 6,5 double bonds. A carbene mechanism is suggested for the reaction.