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 Os₃(CO)₉(μ₃-η²,η²,η²-C₆₀) (OsF1), Os₃(CO)₈(P(CH₃)₃)(μ₃-η²,η²,η²-C₆₀) (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 C₆₀ in a π-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 σ−π-type coordinated compounds. A third electron reduction produces the Os₃(CO)₉(μ₃-η²,η²,η¹-C₆₀)^3- and Os₃(CO)₈(P(CH₃)₃)(μ₃-η²,η²,η¹-C₆₀)^3- complexes, while a fourth electron reduction produces the Os₃(CO)₉(μ₃-η²,η¹,η¹-C₆₀)^4- and Os₃(CO)₈(P(CH₃)₃)(μ₃-η²,η²,η¹-C₆₀)^4- complexes. Our reduction potentials are calculated, in qualitatively good agreement with experimental data obtained using cyclic voltammetry.