Synthesis and characterization of μ3-η2,η2,η2-C60 trirhenium hydride cluster complexes

The reaction of C-60 With Re-3(mu -H)(3)(CO)(11)(NCMe) in refluxing chlorobenzene produces Re-3(mu -H)(3)(CO)(9)(mu (3)-eta (2),eta (2),eta (2)-C-60) (1) in 50% yield. Initial decarbonylation of 1 with Me3NO/ MeCN followed by reaction with PPh3 in boiling chlorobenzene affords Re-3(mu -H)(3)(CO)(8)(PPh3)-(mu (3)-eta (2),eta (2),eta (2)-C-60) (2) in a low yield (26%). Treatment of 1 with PhCH2N=PPh3 at room temperature gives a benzyl isocyanide substituted product Re-3(mu -H)(3)(CO)(8)(CNCH2Ph)(mu (3)-eta (2),eta (2),eta (2)-C-60) (3) in 53% yield. Compounds 1, 2, and 3 have been isolated as crystalline solids and characterized by spectroscopic (infrared, mass, H-1, P-31 and C-13 NMR) and analytical data. The structure of 3 has been determined by a single-crystal X-ray diffraction study. The C-60 ligand is coordinated to the trirhenium triangle in a mu (3)-eta (2),eta (2),eta (2) 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 C-60-mediated electron transfer to the trirhenium center takes place in 1(2-) species for 1 and 2(3-) for 2.