Reaction of [70]Fullerene with Tetraethyl Methylenediphosphonate or Diethyl (Cyanomethyl)phosphonate Revisited

The reaction of C 70 with CH 2 (PO 3 Et 2 ) 2 or CH 2 (PO 3 Et 2 )CN in the presence of NaH has been reinvestigated. The reaction of C 70 with the former phosphonate affords five products. Products 1 – 3 have molecular structures C 70 >CH(PO 3 Et 2 ), whereas products 4 and 5 have molecular structures C 70 >C(PO 3 Et 2 ) 2 . In contrast, only one product 6 , with a molecular structure C 70 >C(PO 3 Et 2 )CN, could be isolated from the reaction of C 70 with CH 2 (PO 3 Et 2 )CN and NaH. Ultrasonication was used to shorten the reaction times and increase the product yields. No product resulting from addition to the C7–C21 bond of C 70 was observed in either cycloaddition reaction. Accordingly, the previously reported major products 3 and 6 , which were assigned as the C7–C21 isomers, should be reassigned as the C1–C2 isomers. This correction is very important for understanding the reactivity of C 70 . Our reassignments are further supported by theoretical calculations. The newly isolated minor products 1 , 2 , and 4 were identified as the C5–C6 isomers. The present work proves that the reactivity order of the bonds in C 70 for these two reactions is C1–C2 > C5–C6. These results resolve the confusion caused by previous incorrect product assignments.