Anionic fullerene-60 complexes of manganese(-I), cobalt(-I), and rhenium(-I):: Thermal and photoinduced electron transfer processes between metal carbonylate anions and C60

Thermal and photochemical reactions of THF solutions of the carbonylate salts A[Mn(CO)(5)], A[CO(CO)(4)], and A[Re(CO)(5)] (A = Na, PPN) with suspensions Of C-60 result in electron transfer to give [C-60](-) and the transient 17-electron, metal-centered radicals Mn(CO)(5), CO(CO)(4), and Re(CO)(5), respectively. However, the ensuing secondary processes vary significantly, depending on the metal and the reaction conditions. With manganese and rhenium, self-coupling Of M(CO)(5) (M = Mn, Re) to give the metal-metal bonded dimers M-2(CO)(10) and coupling of M(CO)(5) with [C-60](-) to give the eta(2) -C-60 complexes A[Mn(CO)(4)(eta(2) -C-60)] both occur under thermal and photochemical conditions. In contrast, the photochemical processes ultimately result also in complete homolysis of the dimers and regeneration of the metal-centered radicals, which then combine with fulleride ion [C-60](-) still remaining in solution to form more of the eta(2)-C-60 complexes. In the case of cobalt, no Co-2(CO)(8) is formed, but the eta(2)-C-60 complex [Co(CO)(3)(eta(2)-C-60)](-) is produced. While the latter is thermally unstable in refluxing THF, undergoing decarbonylation to the previously reported mixed metal fulleride compound NaCoC60.3THF, it is thermally stable under photochemical conditions at room temperature. Spectroscopic evidence suggests that much of the negative charge in [Mn-(CO)(4)(eta-C-60)](-) is delocalized onto the fullerene ligand; as a result, the eta(2)-C-60-Mn bond is unusually strong and the complex [Mn(CO)(4)(eta(2)-C-60)](-) is very stable, exhibiting little of the chemistry associated with either neutral eta(2)-C-60 complexes or the analogous [Mn(CO)(5)](-).