Geometric and electronic structures of Os3(CO)9(μ3-η2,η2,η2-C60), Os3(CO)8(P(CH3)3)(μ3-η2,η2,η2-C60), and their anions (Q = -1 to -4):: reduction-induced conversion of π to σ C60-metal complexes

The geometries and electronic structures of Os-3(CO)(9)(mu(3)-eta(2),eta(2),eta(2)-C-60) (OsF1), Os-3(CO)(8)(P(CH3)(3))(mu(3)-eta(2),eta(2),eta(2)-C-60) (OsF2), and their mono-, di-, tri-, and tetra-anions were calculated using a density functional method. Our calculations show that all three Os atoms are coordinated to C-60 in pi-type mode for the mono- and dianions, as well as in the neutral OsF1 and OsF2 complexes, but that third and fourth electron reductions form mixed sigma-pi-type coordinated compounds. A third electron reduction produces the Os-3(CO)(9)(mu(3)-eta(2),eta(2),eta(1)-C-60)(3-) and Os-3(CO)(8)(P(CH3)(3))(mu(3)-eta(2),eta(2),eta(1)-C-60)(3-) complexes, while a fourth electron reduction produces the Os-3(CO)(9)(mu(3)-eta(2),eta(1),eta(1)-C-60)(4-) and Os-3(CO)(8)(P(CH3)(3))(mu(3)-eta(2),eta(2),eta(1)-C-60)(4-) complexes. Our reduction potentials are calculated, in qualitatively good agreement with experimental data obtained using cyclic voltammetry.