Unexpected fullerene dimerization via [5,6]-bond upon functionalization of C(s)-C70(CF3)8 by the Bingel reaction

The Bingel reaction of the C(s) isomer of C(70)(CF(3))(8) has been found to yield two C(70)(CF(3))(8)C(CO(2)Et)(2)] monoadducts and one C(70)(CF(3))(8)C(CO(2)Et)(2)](2) bisadduct as its major products. Malonate addition occurs at those 6,6]-bonds that radiate from the polar pentagons of the C(70)(CF(3))(8) cage. Unexpectedly, X-ray single crystal analysis reveals dimerization of the above substances during crystallization, providing two isomers of {C(70)(CF(3))(8)C(CO(2)Et)(2)]}(2), one isomer of {C(70)(CF(3))(8)C(CO(2)Et)(2)](2)}(2) and {C(70)(CF(3))(8)}(2). This dimerization represents 2+2]-cycloaddition via 5,6]-bonds and results in functionalization patterns resembling several known C(70)X(10) derivatives.