Synthesis and Characterization of μ₃-η²,η²,η²-C₆₀ Trirhenium Hydrido Cluster Complexes

The reaction of C₆₀ with Re₃(μ-H)₃(CO)₁₁(NCMe) in refluxing chlorobenzene produces Re₃(μ-H)₃(CO)₉(μ₃-η²,η²,η²-C₆₀) (1) in 50% yield. Initial decarbonylation of 1 with Me₃NO/MeCN followed by reaction with PPh₃ in boiling chlorobenzene affords Re₃(μ-H)₃(CO)₈(PPh₃)(μ₃-η²,η²,η²-C₆₀) (2) in a low yield (26%). Treatment of 1 with PhCH₂NPPh₃ at room temperature gives a benzyl isocyanide substituted product Re₃(μ-H)₃(CO)₈(CNCH₂Ph)(μ₃-η²,η²,η²-C₆₀) (3) in 53% yield. Compounds 1, 2, and 3 have been isolated as crystalline solids and characterized by spectroscopic (infrared, mass, ¹H, ³¹P, and ¹³C NMR) and analytical data. The structure of 3 has been determined by a single-crystal X-ray diffraction study. The C₆₀ ligand is coordinated to the trirhenium triangle in a μ₃-η²,η²,η² bonding mode, and the benzyl isocyanide ligand occupies an axial position of a rhenium atom. Electrochemical properties of 1 and 2 have been studied by cyclic voltammetry (CV) in chlorobenzene (CB) solutions. The general features of CV curves have revealed four reversible redox couples for 1 and 2 in the CB potential window. The CV results suggest that a C₆₀-mediated electron transfer to the trirhenium center takes place in 1^2- species for 1 and 2^3- for 2.