A spin crossover phenomena is observed in an anionic (Bu4N+){Co(Ph3P)}(2)(mu(2)-Cl-) (mu(2)-eta(2),eta(2)-C-60)(2). 2C(6)H(14) (1) complex in which two cobalt atoms bridge two fullerene molecules to form a dimer. The dimer has a triplet ground state with two weakly coupling Co-0 atoms (S = 1/2). The spin transition realized above 150 K is accompanied by a cobalt-to-fullerene charge transfer that forms a quintet excited state with a high spin Co-I (S = 1) and C-60(center dot-) (S = 1/2).