Formation of C60F48 and fluorides of higher fullerenes

The effect of contact times and temperatures on fluorination of [60]fullerene by fluorine gas has been analysed by Knudsen cell mass spectrometry. The main product ranges from C60F38/40(4 h, 70 °C) to C60F48(16 h, 315 °C), showing that some control of product according to conditions is possible. The IR spectrum for C60F48(which is white, and crystallises from chloroform or dichloromethane as large colourless prisms) shows fine structure with sharp bands at 1238, 1215, 1199, 1170, 1142, 1126, 771, 754, 724, 650 and 603 cm–1. The 19F NMR spectrum (CDCl3) duplicates precisely that reported in the literature, but couplings not previously observed are evident by 2D (COSY) analysis, thereby confirming further the structure. Fluorination of a sample containing [70]- and higher fullerenes gives rise to C74F44–56, C78F54–60 and C84F56–62. C60F48 is stable towards chlorinated hydrocarbons, but is rapidly degraded by THF, ether and acetone. With benzene and alkylbenzenes, coloured charge transfer-complexes are formed which exhibit a bathochromic shift with increased alkyl substitution of the benzene ring; from toluene solution thick, red needles may be obtained and these slowly become colourless on standing as toluene is lost from the lattice.