Effective derivatization and extraction of insoluble missing lanthanum metallofullerenes La@C_2n (n = 36-38) with iodobenzene

Extraction of insoluble metallofullerenes, La@C_2n (n = 36-38), was conducted with dichlorobenzene, chlorobenzene, and iodobenzene as a solvent under reflux condition. When iodobenzene was used, La@C_2n (n = 36-38) was successfully extracted as the corresponding phenyl adducts, such as La@C₇₂(C₆H₅), La@C₇₄(C₆H₅), and La@C₇₆(C₆H₅). The number of isomers of corresponding adducts, La@C₇₂(C₆H₅) and La@C₇₄(C₆H₅), were reduced to one-third of that in 1,2,4-trichlorobenzene extracts, which was reported previously. Based on the spectroscopic analysis, the carbon cages of La@C₇₂(C₆H₅) and La@C₇₄(C₆H₅) were deduced to be La@C₂(10612)-C₇₂(C₆H₅) and La@D_3h-C₇₄(C₆H₅), respectively. The addition site carbon possessing very high radical character suggests that the corresponding adducts were produced by the addition of phenyl radical generated from iodobenzene on metallofullerenes.