Isolation of Two Seven-Membered Ring C 58 Fullerene Derivatives: C 58 F 17 CF 3 and C 58 F 18

Abstract

Fluorination of C 60 at 550°C leads to milligram quantities of two stable fullerene derivatives with 58-carbon cage structures: C 58 F 18 and C 58 F 17 CF 3 . The compounds were characterized by mass spectrometry and fluorine nuclear magnetic resonance spectroscopy, and the data support a heptagonal ring in the framework. The resulting strain, which has hindered past attempts to prepare these smaller quasi-fullerenes, is mitigated here by hybridization change of some of the carbons in the pentagons from sp 2 to sp 3 because of fluorine addition. The loss of carbon from C 60 is believed to occur via sequential fluorine addition to a C–C single bond and an adjacent C[dbond]C bond, followed by loss of a :CF 2 carbene.