Radical reactions of C-60 dimer connected by a silicon bridge and single bond (C60SiPh2C60) were studied by EPR-spectroscopy. Attack of phosphoryl radicals or 2,2,6,6-tetramethylpiperidine-N-oxyI on the silicon atom leads to radical substitution of the fullerene and formation of a new fullerenyl radical, the structure of the former being confirmed by quantum-chemical calculations (DFT). The formation of only one type of spin-adduct on addition of phosphoryl radicals to the fullerene core is associated with small distortion of the fullerene cage in C60SiPh2C60. Geometry of fullerene core in dimer differs only slightly from C-60 owing probably to flexibility of Si-C and C-C bonds which share a five-membered ring. (C) 2004 Published by Elsevier B.V.