OXIDATION OF BUCKMINSTERFULLERENE WITH M-CHLOROPEROXYBENZOIC ACID - CHARACTERIZATION OF A C-S ISOMER OF THE DIEPOXIDE C60O2

In order to assess the oxidative stability of C-60 and to prepare precursors of fullerene polymerization, the products that are obtained by the oxidation of C-60 With m-chloroperoxybenzoic acid have been compared with those produced by photooxygenation or by ozonolysis. A wider and more readily handled set of products are obtained by the m-chloroperoxybenzoic acid oxidation. Ad three processes produce the previously characterized epoxide. The m-chloroperoxybenzoic acid oxidation produces sufficient quantities of the higher oxide C60O2 so that it has been structurally characterized. The C-13 NMR spectrum of C60O2 indicates that the sample is isomerically pure and that it is one of three possible isomers with C-8 symmetry. C60O2 reacts with Ir(CO)CI(PPh(3))(2) to form black crystals of (eta(2)-C60O2)Ir(Co)Cl(PPh(3))(2) . 5C(6)H(6). A structure determination by X-ray diffraction shows that the structure consists of the fullerene bound to the iridium complex in the expected eta(2) fashion, but that the oxygen atoms are disordered over seven sites of varying occupancy. Additionally there is exchange disorder that involves the carbon monoxide and chloride ligands. Despite these problems, the structure can be analyzed to give information on the structure of this isomer of C60O2. This dioxide is a fullerene diepoxide with both oxygen atoms positioned over 6:6 ring junctions on a common six-membered face of the carbon cage. Contrary to some earlier experimental and theoretical work, the fullerene core has resisted rupture in the oxidative process that forms this dioxide.