Synthesis and Characterization of μ3222-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)93222-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)(μ3222-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)(μ3222-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 μ3222 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 12- species for 1 and 23- for 2.