C 180 O 2 is synthesized simply by heating a mixture of C 60 and C 60 O 1−3 . Electrospray ionization generates doubly charged anions that are assigned as C 120 O 1−6 and C 180 O 2−6 . From C 60 O 2+2 C 60 → C 180 O 2 , we propose a V-shaped structure for C 180 O 2 which retains the bonding sites of the two oxygen atoms in C 60 O 2 . Under similar reaction conditions, adducts containing C 70 and C 70 O building blocks are not observed. Laser desorption ionization mass spectra of C 70 O indicate that the CO bond in C 70 O is weak, providing a plausible account for the difficulty in the formation of C 130 O and C 140 O.