Synthesis and characterization of Ir(H)(CO)(PEt3)(2)(eta(2)-C-60)

Abstract

The title complex, Ir(H)(CO)(PEt3)(2)(eta(2)-C-60) (2), has been prepared by the reaction of excess C-60 (4 equiv) with a tetrairidiurn complex Ir-4(CO)(8)(PEt3)(4) (1) in refluxing chlorobenzene in 40% yield as green crystals. Compound 2 has been characterized by cyclic voltarnmetry (CV), spectroscopic methods (mass, IR, H-1 and P-31 NMR), and a single crystal X-ray diffraction study. The molecular structure reveals that the iridium atom of 2 is coordinated by two axial ligands of a hydrogen atom and a carbonyl group, and three equatorial ligands of two phosphorus atoms and an eta(2)-C-60 moiety. The CV study exhibits three reversible one-electron redox waves for the successive reductions of 2, together with additional four redox waves due to free C60 reductions, which was formed by decomposition of 2 in the reduced states. The three reversible redox waves of 2 are shifted to more negative potentials by ca. 270 mV compared to free C-60, reflecting both metal-to-C-60 pi-back-donation and the electron-donating nature of the two phosphorus ligands.