(cyclopentadienyl)chromiumtricarbonyl dimers as a source of metal-centered free-radicals to form stable η2-bonded spin-adducts with fullerenes

Abstract Spin-adducts ( I ,  IIb – c ) of C 60 and C 70 with metal-centered free radicals CpCr(CO) 3 ( I ,  IIa ) have been generated in toluene via interaction between fullerenes and the weakly metal–metal bonded dimeric complexes [CpCr(CO) 3 ] 2 (Cp = η 5 -C 5 H 5 ( I ); Cp = η 5 -C 5 Me 5 ( II )). Their structures have been investigated using ESR spectroscopy and DFT-PBE calculations and η 2 -bonding to the C C bond between two hexagons in C 60 has been established. Calculations have been extended to investigate the nature of the intermediate η 2 -coordinated toluene chromium complexes ( I ,  IId ).